DC7
July 22, 2020, 10:06pm
1
Hi there!!!
My matrix has 6 columns. I want to multiply each column with a different value. Suppose, the first column multiplied by 25674, second column multiplied by 23123, third column multiplied by 675343, etc...
How can I do that? Is there any easy way if I have to multiply in the same way for around 100 columns?

Best,
DC7

FJCC
July 22, 2020, 10:46pm
2
This seems a little crazy but it is all I could think of.

```
MAT <- matrix(1:20, nrow = 4)
MAT
#> [,1] [,2] [,3] [,4] [,5]
#> [1,] 1 5 9 13 17
#> [2,] 2 6 10 14 18
#> [3,] 3 7 11 15 19
#> [4,] 4 8 12 16 20
MultVec <- c(2, 0.5, 0.1, 3, 10)
MultMAT <- mapply(FUN = `*`, as.data.frame(MAT), MultVec)
MultMAT
#> V1 V2 V3 V4 V5
#> [1,] 2 2.5 0.9 39 170
#> [2,] 4 3.0 1.0 42 180
#> [3,] 6 3.5 1.1 45 190
#> [4,] 8 4.0 1.2 48 200
```

^{Created on 2020-07-22 by the reprex package (v0.2.1)}

1 Like

DC7
July 22, 2020, 10:59pm
3
Hi @FJCC ! How can I round of all the values within the dataframe that generated after the multiplication?

Thanks
DC7

FJCC
July 22, 2020, 11:05pm
4
MultMAT is a matrix and you can do rounding with the apply() function.

```
apply(MultMAT, MARGIN = 2, round, digits = 2)
```

DC7
July 22, 2020, 11:11pm
5
Thanks @FJCC
By the time I have found this works : `round(MultMAT, digits=0)`

Best,
DC7

DC7
July 23, 2020, 12:54pm
6
How can I multiply all the columns with a constant value (e.g. 1 million) ?

Best
DC7

system
Closed
August 13, 2020, 1:04pm
8
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