Subtract a row of values across many rows

user_13097847 0
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I have a dataset that simplifies to something like this, let's call that dataset B

V1      V2 V3 V4
sample1 1  2  3
sample2 4  5  6 
sample3 7  8  9

then I have another separate row (on its own) called blank, it would look something like this.

V1    V2  V3  V4
blank 0.5 1.0 1.5

I would like to subtract blank to all the rows of B. So far I've tried:

B[,2:ncol(B)] <- lapply(B[,2:ncol(B)], function(x) x - blank[,2:ncol(blank)])

B[,2:ncol(B)] <- sweep(B[,2:ncol(B)], 1, blank[,2:ncol(blank)])

B[,2:ncol(B)] <- B[,2:ncol(B)] - blank[,2:ncol(blank)])

B[,2:ncol(B)] <- for(i in 1:nrow(B)){B[ i ,2:ncol(B)] - blank[,2:ncol(B)]}

None of which would work. first one tells me that "replacement element 1 is a matrix/data of 1 row, need 3". Second one tells me "STATS is longer than the extent of 'dim(x)[MARGIN]'", changing margin into 2 does not solve the problem. The third one says "‘-’ only defined for equally-sized data frames". The fourth one returns me a blank matrix.

I've looked through the forum to the best of my ability, but they are limited to applying only one value across the entire dataset, I would like to subtract a whole row of values across the rest of the rows in a dataset.

The end result should look like this (no rounding required).

V1      V2  V3  V4
sample1 0.5 1.0 1.5
sample2 3.5 4.0 4.5
sample3 6.5 7.0 7.5
subtraction rows r
2 Answers

You can subtract the one row from all rows of the second dataframe by repeating the one row as many times as there are rows in the second dataframe and simply subtract those two dataframe like below.

df1 <- t(data.frame(c(1,2,3), c(4,5,6), c(7,8,9)))
df2 <- data.frame(.5, 1, 1.5)
df1[,]-df2[rep(1,3),] # Note that inside the rep i am creating 3 rows if you have
#more rows you need to change 3 to number of rows you have
user_58547310

We can use sweep : 

B[-1] <- sweep(B[-1], 2, unlist(blank[-1]), `-`)
B
#       V1  V2 V3  V4
#1 sample1 0.5  1 1.5
#2 sample2 3.5  4 4.5
#3 sample3 6.5  7 7.5

Or using transpose

B[-1] <- t(t(B[-1]) - unlist(blank[-1]))
user_39629140
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