Failed to use dimensions in a list

[Carlos_Cajas]

I have a list of dataframes that I want to convert two columns to numeric in each object of the list.

This is an example of the list I have:

y <- list(data.frame(Timestamp=c("2016-11-14","2016-11-14","2016-11-14","2016-11-14"),
                           x1=as.character(c(6.225462,5.684068,4.849579,5.223110)),
                           x2=as.character(c(1.362822,1.069084,0.756673,0.950383))),
             data.frame(Timestamp=c("2016-11-14 19:00:00","2016-11-14 19:10:00","2016-11-14 19:20:00","2016-11-14 19:30:00"),
                           x1=as.character(c(6.225462,5.684068,4.849579,5.223110)),
                           x2=as.character(c(1.362822,1.069084,0.756673,0.950383))))

I want to convert columns x1 and x2 of each object of the list to a numeric value with as.numeric but keeping the list.

I tried with this:

y[,-1] <- lapply(y[,-1] , as. numeric)

But this code doesn't work. I get the error

Error in y[, -1] : incorrect number of dimensions

I know y[,-1] would work in a single dataframe but I'm not sure how to handle it in a list.

Please some help.

[gitdemont]

Hi,

It is because y is a list of 2 data.frames as sub-elements.
So, for instance, if you want to access the 1st sub element of y you need to use y[[1]] and not y[, 1]
Then, let's say that df is this first sub-element (df <- y[[1]])
If you want to convert every columns exept 1st one you can not do it with as.numeric(x[, -1]) because x[, -1] is 2 columns.
So you need to loop over columns to do the conversion

lapply(y, FUN = function(df) {
  df[, -1] = apply(df[, -1], 2, FUN = function(col) as.numeric(col))
  df
})

[nirgrahamuk]

library(tidyverse)
map(y,~ .x %>% mutate(across(starts_with("x"),as.numeric)))

[Carlos_Cajas]

Thanks a lot!!

I was doing that at the beginning but I was wrong with the apply function, so I give up.

Thanks again!!

[Carlos_Cajas]

Thanks!!

This works too!!

I tried both solutions.