Question

I need to skip the all the rows with same column one, if column 2 is empty and then for others I need to calculate percentage of column 4 over column 3?

Input:

T75PA       2   0   
T75PA   kk  4   1   
T240P       4   3   
T240P   test    3   3   
T240P   test2   3   1   
T245P   rr  8   1   
T245P   rr  33  1   
T226PA  fg  4   2   
T226PA  g   51  38  
T226PA  e   41  34

Output

T245P   rr  8   1   0.125
T245P   rr  33  1   0.03030303
T226PA  fg  4   2   0.5
T226PA  g   51  38  0.745098039
T226PA  e   41  34  0.829268293

Answer 1

awk '
    NR==FNR {if (NF < 4) blank[$1]; next}
    $1 in blank {next}
    {$(NF+1) = $4/$3; print}
' datafile datafile | column -t

Since you say now that the field separator is tab:

awk '
    BEGIN {OFS = FS = "\t"}
    NR==FNR {if ($2 == "") blank[$1]; next}
    $1 in blank {next}
    {$5 = $4/$3; print}
' datafile datafile