Replace loop with one of the functions of the "apply" family

Question

I have data.frames in lists and, normally, when I want to center data, I use a loop (as seen in the example below). I would like to use some function of the "apply" family, but I can not figure out how to write the code.

An example of my data:

env <- list (data.frame(a=c(-1.08, -1.07, -1.07),
                        b=c( 4.61,  4.59,  4.59),
                        c=c( 3.46,  3.56,  3.52)),
             data.frame(a=c( 3.93,  3.94,  3.92),
                        b=c(-6.69, -6.72, -6.68),
                        c=c( 3.04,  3.08,  3.03)))

The values I will use to center them:

d <- c(a=10.20, b=-10.91, c=11.89)

The type of loop that I commonly use:

for(i in 1:length(env)) {
    env[[i]][, 1] <- env[[i]][, 1] - d[1]
    env[[i]][, 2] <- env[[i]][, 2] - d[2]
    env[[i]][, 3] <- env[[i]][, 3] - d[3]
}

Is there a way to use a function of the "apply" family to do the same thing I did in the above loop?

Answer 1

There are two things you can simplify here: looping over the list elements and subtracting every value in d separately.

To replace for loop you can use lapply ("l" as we're iterating over the list).

# Run function for every element i in list env
lapply(env, function(i))

To simplify subtraction you can:

1. Transpose dataframe t(i)
2. Perform subtraction t(i) - d
3. Transpose it back t(t(i) - d)

So final code would be:

lapply(env, function(i) t(t(i) - d))