Column sum based on conditions

Question

I had a problem when summing columns based on condition. Here, summing columns means d23+d24+d25+d26+..+d31 . Below is part of my dataframe.

      d23  d24  d25   d26    d27    d28    d29    d30    d31
854 -0.60 4.11 8.52  0.90  -7.99 -10.27  -8.32  -6.79 -11.71
855 -1.14 2.66 8.14  0.11  -8.96 -11.25  -9.17  -7.84 -12.53
856 -1.16 0.71 5.45 -1.65 -10.72 -11.18 -11.58 -10.44 -14.29
857  0.08 5.36 9.59 -0.22  -9.79  -9.47  -9.44  -7.67 -10.57
858 -0.95 4.86 8.18 -4.03 -12.15 -11.19 -11.37  -9.47 -13.90
859 -0.70 3.72 8.60  1.87  -6.99  -9.77  -7.84  -6.20 -11.31

As you can see, there are positive and negative values. I want to sum across columns in such a way, if the value is positive, the set it as zero; if the value is negative, then take the absolute value of this value. Finally, sum across columns and create a new column.

Any idea how can I realize that?

Answer 1

One possibility could be:

colSums(abs(df) * (df < 0))

  d23   d24   d25   d26   d27   d28   d29   d30   d31 
 4.55  0.00  0.00  5.90 56.60 63.13 57.72 48.41 74.31