R:as.numeric using grep()

Question

quick question. I have a table (Data) with a series of columns having similar colnames colnames(Data):

[Sum_Flag_x_30,Sum_Flag_y_60,...Sum_Flag_z_n].

I ideally want to write a simple code to get all of these into numeric format (as.numeric). Tried with:

Data[,grep("Sum_Flag",colnames(Data),value=T)] <- as.numeric(Data[,grep("Sum_Flag",colnames(Data),value=T)]

but it's not working and I get the following error:

Error in [<-.data.table(*tmp*, , grep("Sum_Flag", colnames(Data), : Supplied 25 items to be assigned to 55057 items of column 'Sum_Flag_x_30'. If you wish to 'recycle' the RHS please use rep() to make this intent clear to readers of your code.

Any clue about this?

Thanks guys Ciao

Your question is unclear.. Do you want to rename the colnames and then change that to numeric? As in, "Sum_Flag_x_30" would become "30"? — eduardokapp
Hi,sorry. I don't want to rename the columns, just want to trasform the class of the data in these columns into numeric (as.numeric(Data$var)), since they are originally imported as chr. — Roberto92

eduardokapp eduardokapp · Accepted Answer · 2021-03-26T12:48:12

All you have to do is use apply. Apply as.numeric() to every column, by doing:

# margin = 2 means that you're applying a function column-wise.
new_data <- apply(Data, MARGIN = 2, as.numeric)

R:as.numeric using grep()

1 Answers