[R] How to pass a variable to a function which use variable name as a parameter

[wong jane]

There are functions which use variable names as parameters in some R
packages. However, if the variable name is stored in another variable, how
can I pass this variable to the function. Taking the "rms" package as an
example:

library(rms)
n <- 1000
age <- rnorm(n, 50, 10)
sex <- factor(sample(c('female','male'), n,TRUE))

y <- rnorm(n, 200, 25)
ddist <- datadist(age, sex)
options(datadist='ddist')
fit <- lrm(y ~ age)
Predict(fit, age, np=4)
options(datadist=NULL)

Here "age" was a variable name passed to Predict() function, but if "age"
was stored in variable "var", that is, var <- "age", how can I pass "var"
to Predict() function? The purpose is that I want to change the parameter
of Predict()  in a loop.

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