There is a dataset 'm', which has 3 columns: 'index', 'old1' and 'old2';
I want to create 2 new columns: 'new1' and 'new2' on this condition:
if 'index'==i, then 'new1'='old1'+add[i].
'add' is a vector of numbers to be added to old columns, e.g. add=c(10,20,30
...)
Like this:
index old1 old2 new1 new2
1 5 6 15 16
2 5 6 25 26
3 5 6 35 36
3 50 60 80 90
Since the actual dataset is huge, I use 'lapply'. I am able to add 1 column:
do.call(rbind, lapply( 1:nrow(m),
function(i) {m$new1[i]=m[i,2]+add[m[i,1]];
return (m[i,])}
))
but don't know how to do for 2 columns at the same time, sth. like this
simply doesn't work:
do.call(rbind,lapply(1:nrow(m),
function(i){ m$new1[i]=m[i,2]+add[m[i,1]];
m$new2[i]=m[i,3]+add[m[i,1]];
return (m[i,])}
))
Could you please tell me how? or any other better approach?
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