I would like to know how can I come up with a lm
formula syntax that would enable me to use paste
together with cbind
for multiple multivariate regression.
In my model I have a set of variables, which corresponds to the primitive example below:
data(mtcars)
depVars <- paste("mpg", "disp")
indepVars <- paste("qsec", "wt", "drat")
I would like to create a model with my depVars
and indepVars
. The model, typed by hand, would look like that:
modExmple <- lm(formula = cbind(mpg, disp) ~ qsec + wt + drat, data = mtcars)
I'm interested in generating the same formula without referring to variable names and only using depVars
and indepVars
vectors defined above.
For example, what I had on mind would correspond to:
mod1 <- lm(formula = formula(paste(cbind(paste(depVars, collapse = ",")), " ~ ",
indepVars)), data = mtcars)
I tried this as well:
mod2 <- lm(formula = formula(cbind(depVars), paste(" ~ ",
paste(indepVars,
collapse = " + "))),
data = mtcars)
paste
with formula but I would like to know how I can combine with cbind
.cbind
with variable names corresponding to one vector and the remaining variables corresponding to another vector.modExample
without having to type variable names.Think it works.
data(mtcars)
depVars <- c("mpg", "disp")
indepVars <- c("qsec", "wt", "drat")
lm(formula(paste('cbind(',
paste(depVars, collapse = ','),
') ~ ',
paste(indepVars, collapse = '+'))), data = mtcars)
All the solutions below use these definitions:
depVars <- c("mpg", "disp")
indepVars <- c("qsec", "wt", "drat")
1) character string formula Create a character string representing the formula and then run lm
using do.call
. Note that the the formula shown in the output displays correctly and is written out.
fo <- sprintf("cbind(%s) ~ %s", toString(depVars), paste(indepVars, collapse = "+"))
do.call("lm", list(fo, quote(mtcars)))
giving:
Call:
lm(formula = "cbind(mpg, disp) ~ qsec+wt+drat", data = mtcars)
Coefficients:
mpg disp
(Intercept) 11.3945 452.3407
qsec 0.9462 -20.3504
wt -4.3978 89.9782
drat 1.6561 -41.1148
1a) This would also work:
fo <- sprintf("cbind(%s) ~.", toString(depVars))
do.call("lm", list(fo, quote(mtcars[c(depVars, indepVars)])))
giving:
Call:
lm(formula = cbind(mpg, disp) ~ qsec + wt + drat, data = mtcars[c(depVars,
indepVars)])
Coefficients:
mpg disp
(Intercept) 11.3945 452.3407
qsec 0.9462 -20.3504
wt -4.3978 89.9782
drat 1.6561 -41.1148
2) reformulate @akrun and @Konrad, in comments below the question suggest using reformulate
. This approach produces a "formula"
object whereas the ones above produce a character string as the formula. (If this were desired for the prior solutions above it would be possible using fo <- formula(fo)
.) Note that it is important that the response argument to reformulate
be a call object and not a character string or else reformulate
will interpret the character string as the name of a single variable.
fo <- reformulate(indepVars, parse(text = sprintf("cbind(%s)", toString(depVars)))[[1]])
do.call("lm", list(fo, quote(mtcars)))
giving:
Call:
lm(formula = cbind(mpg, disp) ~ qsec + wt + drat, data = mtcars)
Coefficients:
mpg disp
(Intercept) 11.3945 452.3407
qsec 0.9462 -20.3504
wt -4.3978 89.9782
drat 1.6561 -41.1148
3) lm.fit Another way that does not use a formula at all is:
m <- as.matrix(mtcars)
fit <- lm.fit(cbind(1, m[, indepVars]), m[, depVars])
The output is a list with these components:
> names(fit)
[1] "coefficients" "residuals" "effects" "rank"
[5] "fitted.values" "assign" "qr" "df.residual"
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With