Separate columns with constant numbers and condense them to one row in R data.frame

Question

I have a data.frame called d. In this data.frame, some columns consist of constant numbers across the rows of the first column: study.name (see bel

Answer 1

d_list <- lapply(split(d,d$study.name), 
                 #Find columns with similar values using sapply and length(unique(cols)) 
                 #then get the 1st row
                 function(x) x[1, sapply(x,function(y) length(unique(y))==1)])
do.call('rbind.data.frame',d_list)

           study.name ESL prof ESL.1 prof.1
Bit.KnoA     Bit.KnoA   1    3     1      3
Bit.KnoB     Bit.KnoB   1    2     1      2
ChandlerA   ChandlerA   1    2     1      2
Mubarak       Mubarak   2   NA     2     NA
SheenA         SheenA   1    2     1      2
Shin.Ellis Shin.Ellis   1    2     1      2
Sun               Sun   2    2     2      2
Trus.Hsu     Trus.Hsu   2    2     2      2