Question

I have many variables having many observations. I have one standard variable. Now, I want to calculate the difference between the standard and observed variables only when the observation is bigger than the standard and summing up all the differences as a separate variables. In addition, the names of the variables that are bigger than the standard in a separate column.

Names   Standard    Das Dss Tri Tet
Aa  32  42  21  45  34
Ab  23  25  43  43  32
Ac  43  34  23  32  23
Ad  23  24  33  12  23
Ae  14  24  12  20  24
Af  43  42  13  12  43
Ag  12  13  22  13  22
Ah  32  32  42  42  23

OUTPUT:

Names   Standard    Das Dss Tri Tet Difference  No_Difference   Names_Difference
Aa  32  42  21  45  34  15  3   Das, Tri, Tet
Ab  23  25  43  43  32  52  4   Das,Dss,Tri,Tet
Ac  43  34  23  32  23  0   0   NA
Ad  23  24  33  12  23  10  2   Das,Dss
Ae  14  24  12  20  24  26  4   Das,Tri,Tet
Af  43  42  13  12  43  0   0   NA
Ag  12  13  22  13  22  22  4   Das,Dss,Tri,Tet
Ah  32  32  42  42  23  20  2   Dss,Tri

Answer 1

Let’s say your data from above is stored in the object df. Then this should work

df2 <- do.call(rbind, apply(df[, -1], 1, function(z) {
        ind <- z[2:5] > z[1]
        return(cbind.data.frame(
                        Difference = sum(z[2:5][ind] - z[1]), 
                        No_Difference = sum(ind), 
                        Names_Difference = paste(colnames(df[3:6])[ind], 
                                collapse = ", ")
                ))
    }))

df <- cbind(df, df2)
df

  Names Standard Das Dss Tri Tet Difference No_Difference   Names_Difference
1    Aa       32  42  21  45  34         25             3      Das, Tri, Tet
2    Ab       23  25  43  43  32         51             4 Das, Dss, Tri, Tet
3    Ac       43  34  23  32  23          0             0                   
4    Ad       23  24  33  12  23         11             2           Das, Dss
5    Ae       14  24  12  20  24         26             3      Das, Tri, Tet
6    Af       43  42  13  12  43          0             0                   
7    Ag       12  13  22  13  22         22             4 Das, Dss, Tri, Tet
8    Ah       32  32  42  42  23         20             2           Dss, Tri

Altough this is not really elegant and it’s not very robust to use integers to index columns, in case the ordering of your variables changes at some point