r-cran-survival 2.36-10-1 / usr / lib / R / library / survival / NEWS.Rd

\name{NEWS}
\title{NEWS file for the surival package}
\section{Changes in version 2.36-10}{
  \itemize{
    \item A variable name was incorrect in survpenal.fit.  This was in a
    program path that had never been traversed until Carina Salt used
    survreg with a psline(..., method='aic') call, leading to a
    "variable not found" message.

    \item Punctuation error in psline made it impossible for a user to
    specify the boundary.knots argument.  Pointed out by Brandon
    Stewart.

    \item Add an "id" variable to the output of survobrien.

    \item The survfitCI routine would fail for a curve with only one
    jump point (a matrix collapsed into a vector).

    \item Fix an error in survfit.coxph when the coxph model has both a
    strata by covariate interaction and a cluster statement.  The
    cluster term was not dropped from the Terms object as it should have
    been, led to a spurious "variable not found" error.   Pointed out
    by Eva Bouguen.
}}

\section{Changes in version 2.36-9}{
  \itemize{
    \item Due to a mistake in my script that submits to CRAN, the fix in
    2.36-8 below was actually not propogated to the CRAN submission.

    \item Fix an error in the Cauchy example found in the survreg.distributions
    help page, pointed out by James Price.

    \item Update the coxph.getdata routine to use the model.frame.coxph
    and model.matrix.coxph methods.

    \item Add the concordance statistic to the printout for penalized models.
}}

\section{Changes in version 2.36-8}{
  \itemize{
    \item Unitialized variable in calcuation of the variance of the
    concordance.  Found on platform cross-checking by Brian Ripley.
    \item Changed testci to use a fixed file of results from cmprsk
    rather than invoking that package on-the-fly.  Suggested by the CRAN
    maintainers.
  }
  }
\section{Changes in version 2.36-7}{
  \itemize{
    \item Due to changes in R 2.13 default printout, the results of many of
    the test programs change in trivial way (one more or fewer digits).
    Update the necessary test/___.Rout.save files.  Per the core team's
    suggestion the dependency for the package is marked as >=2.13.
  }}
  
\section{Changes in version 2.36-6}{
  \itemize{
    \item An example from A Drummond caused iteration failure in
    coxph: x=c(1,1,1,0,1, rep(0,35)), time=1:40, status=1.  The first
    iteration overshoots the solution and lands on an almost perfectly
    linear part of the loglik surface, which made the second iteration
    go to a huge number and exp() overflows.  A sanity check routine
    coxsafe is now invoked on all values of the linear predictor.
    
    \item 1 April: Fix minor bug in survfit.  For left censored data
    where all the left censored are on the very left, it would give a
    spurious warning message when trying to create a 0 row matrix that
    it didn't need or use.  Pointed out by Steve Su.
    
    \item 31 March 2011: One of the plots in the r_sas test was wrong
    (it's been a long time since I visually checked these).  The error
    was in predict.survreg; it had not taken into account a change in
    R2.7.1: the intercept attribute is reset to 1 whenever one
    subscripts a terms object, leading to incorrect results for a model
    with "-1" in the formula and a strata(): the intercept returned
    when removing the strata.  I used this opportunity to move most of
    the logic into model.frame.survreg and model.matrix.survreg
    functions.  Small change to the model.frame.coxph and
    model.matrix.coxph functions due to a better understanding of
    xlevels processing.
    
    \item Round off error issue in survfit: it used both unique(time)
    and table(time), and the resulting number of unique values is not
    guarranteed to be the same for times that differ by a tiny amount.
    Now times are coverted to a factor first.  Peter Savicky from the R
    core team provided a nice discussion of the issue and helped me
    clarify how best to deal with it.  The prior fix of first rounding
    to 15 digits was good enough for almost every data set -- except the
    one found by a local user just last week.
    
    \item Round off error in print.survfit pointed out by Micheal Faye.
    If a survival value was .5 in truth, but .5- eps due to round off
    the printed median was wrong. But it was ok for .5+eps. Simple
    if-then logic error.
    
    \item Re-fix a bug in survfit.  It uses both unique and table in
    various places, which do not round the same; I had added a
    pre-rounding step to the code.  A data set from Fan Chun showed that
    I didn't round quite enough. But the prior rounding did work for a
    time of 2 vs (sqrt(2))^2: this bug is very hard to produce.  I now
    use as.numeric(as.character(factor(x))), which induces exactly the
    same rounding as table, since it is the same compuation path.

    \item Further changes to pspline.  The new Boundary.knots argument
    allows a user to set the boundary knots inside the range of data.
    Code for extrapolation outside that range was needed,
    essentially a copy of the code found in ns() for the same issue.
    Also added a psplineinverse function, which may be useful with
    certain tt() calls in coxph.
    
    \item 10 Mar 2011: Add the capablilty for time-dependent
    transformations to coxph, along with a small vignette describing use
    of the feature.  This code is still incompletely incorporated in
    that the models work but other methods (residuals, predict, etc) are
    not yet defined.
    
    \item 8 Mar 2011: Expand the survConcordance function.  The function
    now correctly handles strata and  time dependent covariates, and
    computes a standard error for the estimate.  All computation is based
    on a balanced binary tree strucure, which leads to computation in
    \eqn{O(n \log_2(n))}{O(n log(n))} time.
    The \code{coxph} function now adds concordance to its output, and
    \code{summary.coxph} displays the result.

    \item 8 Mar 2011: Add the "reference" option to predict.coxph, a
    feature and need pointed out by Stephen Bond.

    \item 4 Mar 2011: Add a makepredictcall method for pspline(), which
    in turn required addition of a Boundary.knots argument to the
    function.
    
    \item 25 Feb 2011: Bug in pyears pointed out by Norm Phillips.  If a
    subject started out with "off table" time, their age was not
    incremented by that amount as they moved forward to the next "in
    table" cell of the result.  This could lead to using the wrong
    expected rate from the rate table.
  }
}

\section{Changes in version 2.36-5}{
  \itemize{
    \item 20 Feb 2011: Update survConcordance to correctly handle case
    weights, time dependent covariates, and strata.

    \item 18 Feb 2011: Bug in predict.coxph found by a user (1 day after
    36-4!).  If the coxph call had a subset and predict used newdata,
    the subset clause was "remembered" in the newdata construction,
    which is not appropriate.
}}

\section{Changes in version 2.36-4}{
\itemize{
  \item 17 Feb 2011: Fix to predict.coxph.  A small typo that only was
  exercised if the coxph model had x=T.  Discovered via induced error in
  the rankhazard package.  Added lines to the test suite to test for
  this in the future.

  \item Removed some files from test and src that are no longer needed.

  \item Update the configure script per suggestion from Kurt H.
  }}
\section{Changes in version 2.36-3}{
  \itemize{

    \item 13 Feb 2011: Add the rmap argument to pyears, as was done for
    survexp, and update the manual pages and examples. Fix one last bug
    in predict.coxph (na.action use).  Passes all the
    tests for inclusion on the next R release.

    \item 8 Feb 2011: Change the name of the new survfit.coxph.fit routine to
     survfitcoxph.fit; R was mistaking it for a survfit method.  Fix
     errors in predict.coxph when there is a newdata argument, including
     adding yet another test program.

   \item 1 Feb 2011: Fix bugs in coxph and survreg pointed out by Heinz
    Tuechler and dtdenes@cogpsyphy.hu, independently, that were the same
    wrong line in both programs.  With interactions, a non-penalized
    term could be marked as penalized due to a mismatched vector length,
    leading to a spurious error message later in the code.
  
  \item 1 Feb 2011: Update survfit.coxph to handle the case of a strata by
    covariate interaction.  All prior releases of the code did this
    wrong, but it is a very rare case (found by Frank Harrell).  Added a
    new test routine coxsurv4.  Also found a bug in [.survfit; for a
    curve with both strata and multiple columns, as produced by
    survfit.coxph, it could drop the n.censored item when subscripting.
    A minor issue was fixed in coxph: when iter=0 the output coefficient
    vector should be equal to the input even when the variance is
    singular. 

  \item 30 Jan 2011: Move the noweb files to a top level directory, out of
    inst/.  They don't need to be copied to binary installs.
    
  \item 22 Jan 2011: Convert the Changelog files to the new inst/NEWS.Rd
    format.
  
  \item 1 Jan 202011: The match.ratetable would fail when passed a data
    frame with a character variable.  This was pointed out by Heinz
    Tuechler, who also did most of the legwork to find it.  It was
    triggered by the first few lines of tests/jasa.R (expect <- ....)
    when options(stringsAsFactors=FALSE) is set. 
 }
}

\section{Changes in version 2.36-2}{
\itemize{
  \item 20 Dec 2010: Add more test cases for survfit.coxph,
    which led to significant updates in the code. 

  \item 18 Nov 2010: Add nevent to the coxph output and printout in
    response to a long standing user request.

  \item 14 Dec 2010: Add an as.matrix method for Surv objects. 

  \item 11 Nov 2010: The prior changes broke 5 packages: the dependencies form a bigger
test suite than mine!  1. Survival curve for a coxph model with sparse
frailty fit; fixed and added a new test case.  2. survexp could fail if 
called from within a function due to a scoping error.  3. "Tsiatis" was once
a valid type (alias for 'aalen')  for survfit.coxph; now removed from the 
documentation but the code needed to be backwards compatable.  The other two
conflicts were fixed in the packages that call survival.  There are still
issues with the rms package which I am working out with Frank H.
 }
}

\section{Changes in version 2.36-1}{
 \itemize{
  \item{27 Oct 2010: Finish corrections and test to the new code. It now passes
the checks.  The predict.coxph routine now does strata and standard errors
correctly, factors propogate through to predictions, and numerous small 
errors are addressed.  Predicted survival curves for a Cox model has been
rewritten in noweb and expanded. Change the version number to 2.36-1.}

  \item{17 Oct 2010: Per a request from Frank Harrell (interaction with his library),
survfit.coxph no longer reconstructs the model frame unless it really needs
it: in some cases the 'x' and 'y' matrices may be sufficient, and may be
saved in the result.  Add an argument "mf" to model.matrix.coxph for more 
efficient interaction when a parent routine has already recovered the model 
frame.
  In general, we are trying to make use of model.matrix.coxph in many of the
routines, so that the logic contained there (remove cluster() calls, pull
out strata, how to handle intercepts) need not be replicated in multiple 
places.}

  \item{12 Oct 2010: Fix a bug in the modified lower limits for survfit (Dory & Korn).
A logical vector was being inadvertently converted to numeric.  Pointed out
by Andy Mugglin.  A new case was added to the test suite. }
 }
}

\section{Changes in version 2.35}{ 
 \itemize{
  \item{15 July 2010: Add a coxph method for the logLik function.  This is used by
the AIC function and was requested by a user.}

  \item{29 July 2010: Fix 2 bugs in pyears.  The check for a US rate table was off
(minor effect on calculations), and there was a call to julian which assumed
that the origin argument could be a vector.  }

  \item{21 July 2010: Fix a problem pointed out by a user: calling survfit with almost
tied times, e.g., c(2, sqrt(2)^2), could lead to an inconsistent result.  Some
parts of the code saw these as 2 unique values per the unique() function, some
as a single value using the results of table().  We now pre-round the input
times to one less decimal digit than the max from .Machine$double.digits.
  Also added the noweb.R processing function from the coxme package, so that
the noweb code can be extracted "on the fly" during installation using
commands in the configure and cleanup scripts.  }

  \item{11 July 2010: A rewrite of the majority of the survfit.coxph code.  The primary
benefits are 1: finally tracked down and eliminated the bug for standard errors
of case weights + Cox survival + Efron method; 2: the individual=TRUE and FALSE
options now use the same underlying code for curves, before there were some
options valid only for one or the other; 3: code was rewritten using noweb 
with a considerable increase in documentation; 4: during the verification
process some errors were found in the test suite and corrected, e.g., a 
typo in my book led to failure of an all.equal test in book4.R.  Similar
to the rewrite for survfit several years ago, the new code has far less use
of .C to help transparency.}

  \item{21 May 2010: Fix bug in summary.survfit.  For a survival curve from a Cox model
with start,stop data, the 'times' argument would generate an error.}

  \item{24 May 2010: Fix an annoyance in summary.survfit.  When the survival data 
had an event or censor at time 0 and summary is called with a times argument,
then my constructed call to approx() would have duplicate x values.  The answer
was always right, but approx has begun to print a bothersome warning message.  
A small change to the constructed argument vector avoids it.}

  \item{7 April 2010: Minor bug pointed out by Fredrik Lundgren.  In survfit if the
method was KM (default) and error = Tsiatis an error message results.  Simple
fix: code went down the wrong branch.}

  \item{24 Feb 2010: Serious bug pointed out by Kevin Buhr.  In Surv(time1, time2,stat)
if there were i) missing values in time1 and/or time2, ii) illegal value
sets with time1 >=time2, and iii) all the instances of ii do not preceed all
the instances of i, then the wrong observation (not the illegal) will be 
thrown out.  Repaired, and a new test added.
  Minor updates to 3 test files: survreg2, testci, ratetable.}

  \item{8 Feb 2010: Bug pointed out by Heinz Tuechler -- if a subscript was dropped from
a rate table the 'type' attribute got dropped, e.g. survexp.usr[,1,,].}

  \item{26 Jan 2010: At the request of Alex Bokov, added the xmax, xscale, and fun
arguments to points.survfit.}

  \item{26 Jan 2010: Fix bug pointed out by Thomas Lumley -- with case weights <1 a Cox 
model with (start, stop) input would inappropriately decide it needed to do
step halving to find a solution, eventually failing to converge.  It was
treating a loglik >0 as an indication of failure, but such values arise for
small case weights. Let L(w) be the loglik for a data set where everyone is
given a weight of w, then L(w)= wL(1) - d log(w) where d=number of deaths in
the data.  For small enough w positivity of L(w) is certain.}

  \item{25 Jan 2010: Fix bug in summary.ratetable pointed out by Heinze Tuechler.  Added
a call to the function to the test suite as well.}

  \item{15 Dec 2009: Two users pointed out a bug that crept into survreg() with a
cluster statement, when a t(x)%*%x was replaced with crossprod.  A trivial
fix, but in response I added another test that more formally checks the
dfbeta residuals and found a major oversight for the case of multiple
strata.  }

  \item{14 Dec 2009: 1.Fix bug in frailty.xxx, if there is a missing value in the levels
it gets counted by "length(unique(x))" (frailty is called before NA
removal.)  2.SurvfitCI had an incorrect CI with case weights, and 3. in
survreg a call to resid instead of residuals.survreg, before the class
was attached.}

  \item{11 Nov 2009: The 'type' argument does not make sense for plot.survfit.  (If 
type='p', should one plot the tops of the step function, the bottoms, or
both?).  Make it explicitly disallowed in response to an R-help query,
rather than the confusing error message that currently arose.}

  \item{28 Oct 2009: The basehaz function would reorder the labels of the strata
factor.  Not a bug really, but a "why do this?"  Unintended consequence of
a character -> factor conversion.}

  \item{1 Oct 2009: Fix a bug pointed out by Ben Domingue.  There was one if-then-else
path into step-halving in the frailty.controldf routine that would refer to
a non-existent variable.  A very rarely followed path, obviously, and with
the obvious fix. The mathematics of the update was fine.}

  \item{30 Sep 2009: For coxph and model.matrix.coxph, re-attach the
attributues lost from the X matrix when the intercept is removed,
i.e., X <- X[,1].  In particular, some downstream libraries depend on
the assign attribute. 
  For predict.coxph remove an earlier edit so that a single variable model
+ type='terms' returns a matrix, not a vector.  This is expected by the 
termplot() function.  It led to a whole lot of changes in the test suite
results, though, due to more "matrix" printouts.}

  \item{4 Sep 2009: Added a model.matrix.coxph and model.frame.coxph methods.  The
model.matrix.default function ceased to work for coxph models sometime
between R 2.9 and 2.9.2 (best guess).  This wasn't picked up in the test
suite but rather by failure of 3 packages that depend on survival.  Also added
a test.  Update CRAN since this broke other's packages.}

  \item{20 Aug 2009: One more fix to predict.coxph.  It needed to use 
delete.response(Terms) rather than Terms, so as to not look for (unnecessarily)
the response variable when the newdata argment is used.  Pointed out by Michael
Conklin.}

  \item{17 Aug 2009: Small bug in survfit.coxph.null pointed out by Frank Harrell.  The
'n' component would be missing if the input data included strata, i.e., the
initial model had used x=TRUE.  He also pointed out the fix.}

  \item{10 June 2009: Fix an error pointed out by Nick Reich, who was the first to use
interval censored data + user defined distribution in survreg, jointly.  There
was no test case and creating one uncovered several errors (but only for this
combination).  All the error cases led to catastrophic failure, highlighting
the extreme rarity of a user requesting this combination.}

  \item{2 June 2009: Surv(time1, time2, status, type='interval') would fail for an NA
status code.  Pointed out by Achim Zeilus.}

  \item{22 May 2009: Allow single subscripts to rate tables, e.g. survexp[1:10: .  
Returns a simple vector of values.  The str() function does this to print out
a short summary.  Problem pointed out by Heinz Tuechler.}

  \item{21 May 2009: Create a test case for factor variables/newdata/predict for coxph 
and survreg.  This led to a set of minor fixes; the code is now in line with
the R standard for model functions.  One consequence is that model.frame.coxph
and model.frame.survreg are no longer needed, so have been removed.}

  \item{20 May 2009: The manual page for survfit was confusing, since it tries to 
document both the standard KM (formula method) and the coxph method.  I've
split them out so that now survfit documents only the basic method and points 
a user the appropriate specialized page.}

  \item{1 May 2009: The anova.coxph function was incorrect for models with a strata
term.  Fixed this, and made chisquare tests the default.}

  \item{22 April 2009: The coxph code had an override to iter and eps, making both of
them more strict for a penalized model.  However, the overall default values
have changed over time, so that these lines actually decreased accuracy - the
opposite of their intent.  Removed the lines.  Also removed the iter.miss and
eps.miss components (on which this check depended) from coxph.control, which
makes that function match its documentation.}

 }
}

\section{Changes in version 2.34 and earlier}{
\subsection{Merge of the TMT source code tree with the Lumley code tree}{
 \itemize{

  \item Issues/decisions in remerging the Mayo and R code: 
  For most of routines, it was easier to start with the Lumley code and add
the Therneau fixes.  This is because Tom had expanded a lot of partial 
matches, e.g., fit$coef in the TT code vs fit$coefficients.  Routines with
substantial changes were, of course, a special case.
  The most common change is an is.R() construct to choose class vs oldClass.
  \item xtras.R: Move anova.coxph and anova.coxphlist to their own
  source files.
  The remainder of the code is R only.

  \item survsum: removed from package

  \item survreg.old: has been removed from the package

  \item survfit.s: 
   Depreciate the "formula with no ~1" option
   Mayo code for [ allows for reordering curves
   Separate out the R "basehaz" function as a separate source file

  \item survfit.km.s: The major change of did not get copied into R, so lots of
changes.  R had "new.time" and Splus 'start.time' for the same argument.  Allow
them both as synonyms.
   The output structure also changed: adapt the new one.  This is mostly some
name changes in the components, removing unneeded redundancies created by
a different programmer. 

  \item survfit.coxph.s:  TMT code finally fixed the "Can't (yet) to case weights" 
problem.  There must have been 10 years been the intent and execution. 

  \item survexp.s:  Add "bareterms" function from R, which replaces a prior use of
  terms.inner (in Splus but not R). 

  \item survdiff.s: R code had the old (incorrect) expected <- sum(1-offset), since
corrected to sum(-log(offset)) . 

  \item{summary.coxph.s: This was a mess, since Tom and I had independently made the
 addition of a print.summary.coxph function.  Below, TMT means that it was the
 choice in the Splus code, TL means that it was the choice in R
	1. Put the coef=T argument in the print function, not summary (TMT)
	2. Change the output's name from coef to coefficients (suggestion of
  Peter Dalgaard).  Also change one column name to Pr(>|z|) for R.
	3. Remove last vestiges of a reference to the 'icc' component (TMT)
	4. Do not include score, rscore, naive.var in the result (TL)
	5. Do include loglik in the result (TMT)
	6. Compute the test statistics (loglik, Wald, etc) in the summary
   function rather than in the print.summary function (TL)
	7. Remove the digits option from summary, it belongs in print.summary.
   (neither)}

  \item{strata.s: R code added a sep argument, this is ok
     R changed the character string NA to as.character(NA).  Not okay
          1. won't work with Splus, 
          2. This is a label, designed for printing, 
	          and so it should be a character string.  }

  \item{residuals.coxph.s: R had added type='partial'.  (Which I'm not very partial to,
  from their statistical properties.  But they are legal, and I assume that
  someone requested them).}

  \item{print.survfit.s: Rewritten as a part of the general survival rewrite.  Created
the function 'survmean' which does most of the work, and is shared by print and
summary, so that the values from 'print' are now available.
   Fix the minmin function: min(NULL) gives NA in Splus, which is the right
answer for a non-estimable median, but Inf in R.  Explicitly deal with this
case, and add a bunch of comments.
   R had the print.rmean option, this has been expanded to a more general
rmean option that allows setting the cutoff point.
   R added a print.n option with 3 choices, my code includes all 3 in the 
output.  }

  \item{lines.survfit.s: 
    The S version has a new block of code for guessing "firstx" more
intellegently when it is missing.  (Or, one hopes is is more intellegent!)}

  \item{coxph.control.s: 
   The R code had tighter tolerances (eps= 1e-9) than Splus (1e-4) and
a higher iterationn count (20 vs 10). 
   Set eps to 1e-8 and iter to 15, mostly bending to the world.  The tighter
iteration is defensible, but I still maintain that a Cox model that takes >10 
iterations is not going to finish if you give it 100.  The likelihood surface
is almost perfectly quadratic near the minimum.  (Not true for survreg by the
way).}

  \item{: In Surv, the Mayo code creates NA's out of invalid status values or
start,stop pairs, rather than a stop and error message.  This is to
allow for example
       coxph(Surv(time1,time2, status).... , subset=(goodlines))
succeed, when "goodlines" is the subset with correct values.}
}
}

\subsection{Older changes}{
 \itemize{
  \item{25SepO7: How embarrassing -- someone pointed out that I had Dave Harrington's
name spelled wrong in the options to survfit.coxph!}

  \item{9Jul07: In a model with offsets, survreg mistakenly omitted the offset
from the returned linear.predictor component.}

  \item{10May07: Change summary.coxph so that it returns an object of class
summary.coxph, and add a print method for that object.}

  \item{22Jun06: Update match.ratetable, so that more liberal matches are now
allowed.  For instance,  'F', 'f', 'female', 'fem', 'FEMA', etc are 
now all considered matches to the dimname "female" in survexp.us.}

  \item{26Apr06: Fix bug in summary.survfit, pointed out by Bob Treder.  With
the times option, the value of n.risk would be wrong for "in between"
times; e.g., the data had events and/or censoring at times 10,
20,... and we asked for printout at time 15.  It should give n.risk at time
20, it was returning the value at time 10. Interestingly, the code had
a very careful treatment of this case, along with an example in the
comments, and the "the right answer is" part of the comment was wrong!
So the code correctly computed an incorrect answer.  Added another
test case to the test suite, survtest2.}

  \item{21Apr06: Fix problem in [.survfit, pointed out by Thomas Lumley.  If
fit <- survfit(Surv(time, status) ~ ph.ecog, lung), then fit[2:1] did
not reorder the output correctly.  I had never tested putting the 
subscripts in non-increasing order.}

  \item{7Feb06: Fix a problem in the coxph iteration (coxfit2.c, coxfit5, agfit3,
agfit5, agexact).  It will likely never catch anyone again, even if I 
didn't fix it.  In a particular data set, beta overshot and step halving
was invoked.  During step halving, a loglik happened to occur that was
within eps of the prior step's loglik --- and the routine decided, erroneously,
that it had converged!  (A nice quadratic curve, a first guess b1 to the 
left of  the desired max of the curve.  The next guess b2 overshot and ends 
up with a lower loglik, on the right side of the max.  Back up to the 
midpoint of b1 and b2, and this guess, still to the right of the max (still
too large) has EXACTLY the same value of y as b1 did, but on the other side
of the max from b1.  "Last two guesses give the same answer, I'm done" said
the routine).}

  \item{27Sep05: Found and fixed a nasty bug in survfit.  When method='fh2' and
there were multiple groups I had a subscripting bug, leading to vectors
that were supposed to be the same length, but weren't, passed into C.
The resulting curves were obviously wrong -- survival precipitously drops 
to zero.}

  \item{5May05: Add the drop=F arg to one subscripting selection in survfit.coxph.
	        temp <- (matrix(surv$y, ncol=3))[ntime,,drop=F] 
If you selected only 1 time point (1 row) in the final output, the code
would fail.  Pointed out by Cindy Crowson.}

  \item{18Apr05: Bug in survfit.turnbull.  The strata variable was not being
filled in (number of points per curve).  So if multiple curves were
generated at once, i.e., with something on the right hand side of ~ in
the formula, all the downstream print/plot functions would not work
with the result.}

  \item{8Feb05: Fix small typo in is.ratetable, introduced on 24Nov04: (Today
was the first time I added to the standard library, and thus ended
up using the non-verbose mode.)}

  \item{8Feb05: Add the data.frame argument to pyears.  This causes the output
to contain a dataframe rather than a set of arrays.  It is useful for
further processing of the data using Poisson regression.}

  \item{7Feb05: Modified print.ratetable to be more useful.  It now tells 
about the ratetable, rather than printing all of its values.}

  \item{8Dec04: Fix a small bug in survfit.turnbull. If there are people left 
censored before the first
time point of any other kind (interval, exact, or right censored),
the the plotted height of the curve from "rightmost left censoring time"
to "leftmost event time", that is the flat tail on the left, was at
the wrong height.
  Added another test to testreg/reliability.s for this.}

  \item{24Nov04: Change is.ratetable to give longer messages}
}
}
}