How can I get the average mean of selected columns

Question

I would like to get the average for certain columns for each row   I have this data   w c 5 6 7 8  x c 1 2 3 4  y c 1 2 3  length y  4 z data frame w x y    Which returns     w x  y 1 5 1  1 2 6 2  2 3 7 3  3 4 8 4 NA   I would like to get the mean for certain columns  not all of them   My problem is that there are a lot of NAs in my data   So if I wanted the mean of x and y  this is what I would like to get back     w x  y mean 1 5 1  1    1 2 6 2  2    2 3 7 3  3    3 4 8 4 NA    4   I guess I could do something like z mean  z x z y  2 but the last row for y is NA so obviously I do not want the NA to be calculated and I should not be dividing by two   I tried cumsum but that returns NAs when there is a single NA in that row   I guess I am looking for something that will add the selected columns  ignore the NAs  get the number of selected columns that do not have NAs and divide by that number   I tried   mean and   average and am completely stumped   ETA  Is there also a way I can add a weight to a specific column

User · Answer

Try using rowMeans   z mean rowMeans z  c  x    y     na rm TRUE     w x  y mean 1 5 1  1    1 2 6 2  2    2 3 7 3  3    3 4 8 4 NA    4

User · Answer

Here are some examples    gt  z mean  lt - rowMeans subset z  select   c x  y    na rm   TRUE   gt  z   w x  y mean 1 5 1  1    1 2 6 2  2    2 3 7 3  3    3 4 8 4 NA    4   weighted mean   gt  z y  lt - rev z y   gt  z   w x  y mean 1 5 1 NA    1 2 6 2  3    2 3 7 3  2    3 4 8 4  1    4  gt    gt  weight  lt - c 1  2    x   1 3   y   2 3  gt  z wmean  lt - apply subset z  select   c x  y    1  function d  weighted mean d  weight  na rm   TRUE    gt  z   w x  y mean    wmean 1 5 1 NA    1 1 000000 2 6 2  3    2 2 666667 3 7 3  2    3 2 333333 4 8 4  1    4 2 000000

[r] How can I get the average (mean) of selected columns

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