CODEWITHSUNDEEP
rcox-regression
Max Gordon
Max Gordon

Reputation: 5467

Cox regression output in xtable - choosing rows/columns and adding a confidence interval

I wan't to export the output from a cox regression to a table that I then can put into my article. I guess the best way to go about it is with xtable:

library(survival)
data(pbc)
fit.pbc <- coxph(Surv(time, status==2) ~ age + edema + log(bili) + 
    log(protime) + log(albumin), data=pbc)

summary(fit.pbc)
library(xtable)
xtable(fit.pbc)

Now I want to do the following to the output:

Thanks in advance!

Upvotes: 6

Views: 6336

Answers (2)

IRTFM
IRTFM

Reputation: 263301

xtable(round(summary(fit.pbc)$conf.int[c(1,3),],3))
#-----------------------------#
% latex table generated in R 2.13.1 by xtable 1.5-6 package
% Sat Oct 15 18:36:04 2011
\begin{table}[ht]
\begin{center}
\begin{tabular}{rrrrr}
  \hline
 & exp(coef) & exp(-coef) & lower .95 & upper .95 \\ 
  \hline
age & 1.04 & 0.96 & 1.02 & 1.06 \\ 
  log(bili) & 2.37 & 0.42 & 2.02 & 2.79 \\ 
   \hline
\end{tabular}
\end{center}
\end{table}

This shows what you see with str on the summary-object

str(summary(fit.pbc))
# snipped
 $ conf.int    : num [1:5, 1:4] 1.0404 2.4505 2.3716 10.8791 0.0815 ...
  ..- attr(*, "dimnames")=List of 2
  .. ..$ : chr [1:5] "age" "edema" "log(bili)" "log(protime)" ...
  .. ..$ : chr [1:4] "exp(coef)" "exp(-coef)" "lower .95" "upper .95"

Upvotes: 3

Josh O&#39;Brien
Josh O&#39;Brien

Reputation: 162321

I'd approach this by first taking a look at how the survival package constructs the table it prints by default.

To find the function that does that printing, examine the class of your fit object, and then look for a print method for that class:

class(fit.pbc)
# [1] "coxph"
grep("coxph", methods("print"), value=TRUE)
# [1] "print.coxph"         "print.coxph.null"   
# [3] "print.coxph.penal"   "print.summary.coxph"

After taking a look at print.coxph, here's what I came up with:

cox  <- fit.pbc

# Prepare the columns
beta <- coef(cox)
se   <- sqrt(diag(cox$var))
p    <- 1 - pchisq((beta/se)^2, 1)
CI   <- round(confint(cox), 3)

# Bind columns together, and select desired rows
res <- cbind(beta, se = exp(beta), CI, p)
res <- res[c("age", "log(protime)"),]

# Print results in a LaTeX-ready form
xtable(res)

Upvotes: 9

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