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rdplyrsapply

Copy values from one table to another, only where second table has specific values

I thought this would be straightforward, but it's been a while since I've looked at R.

I have two tables, and I want to make a third table with values from the first based on values from the second. (I want the numbers from table 1, anytime the corresponding row/column from table 2 has a "1")

I was thinking sapply or lapply would probably be what I need, or something from ? Just not sure how.

Table 1 (df1):

row  sample.1  sample.2  sample.3
1       55       6788      4003
2     9000        135      1200
3     3400       2000      7500
4       92        348       227  
5     4286       2731      6298

Table 2 (df2):

row  sample.1  sample.2  sample.3
1        0          1         1
2        1          0         0
3        1          1         1
4        0          0         0  
5        1          1         1

Table 3 ( df3 - desired output):

row  sample.1  sample.2  sample.3
1        0       6788      4003
2     9000          0         0
3     3400       2000      7500
4        0          0         0  
5     4286       2731      6298
Solution

  • An easier option would be an elementwise multiplication as these are numeric columns and because any number multiplied by 0 returns 0 while those multiplied by 1 gives the number itself (assuming both datasets have same dimensions 

    df1 * df2

    If 'row' is the first column, subset the datasets by removing the first column and cbind with the first column of any of the datasets

    cbind(df1[1], df1[-1] * df2[-1])