R help - Feb 2012 - dividing values of each column in a dataframe

Hey Guys

I want to divide(numerically) all the columns of a data frame by
different numbers. Here is what I am  doing but getting a weird error.
The values in each column are not getting divided by the corresponding
value in the denominator vector instead by the alternative values. I
am sure I am messing up something.

Appreciate your help
-Abhi

head(counts)
               WT_CON WT_RB MU_CON MU_RB
row1       839   180    477   187


head(counts/c(2,3,4,5))
               WT_CON    WT_RB    MU_CON    MU_RB
row1      419.50000  45.0000  238.5000  46.7500

On Feb 6, 2012, at 2:22 PM, Abhishek Pratap wrote:
> Hey Guys
>
> I want to divide(numerically) all the columns of a data frame by
> different numbers. Here is what I am  doing but getting a weird error.
> The values in each column are not getting divided by the corresponding
> value in the denominator vector instead by the alternative values. I
> am sure I am messing up something.
>
> Appreciate your help
> -Abhi
>
> head(counts)
>               WT_CON WT_RB MU_CON MU_RB
> row1       839   180    477   187
>
>
> head(counts/c(2,3,4,5))
>               WT_CON    WT_RB    MU_CON    MU_RB
> row1      419.50000  45.0000  238.5000  46.7500
The argument recycling is going to be done on a column basis. You  
apaear to expect it to be done on a row basis. For that you need apply

Probably:

t( apply(counts, 1, "/", c(2,3,4,5)) )


But untested in absence of example.

---
David Winsemius, MD
West Hartford, CT

On 06-02-2012, at 20:22, Abhishek Pratap wrote:
> Hey Guys
> 
> I want to divide(numerically) all the columns of a data frame by
> different numbers. Here is what I am  doing but getting a weird error.
I don't think you are getting an error.
You are getting an unexpected result (you think).
> The values in each column are not getting divided by the corresponding
> value in the denominator vector instead by the alternative values. I
> am sure I am messing up something.
> 
> Appreciate your help
> -Abhi
> 
> head(counts)
>               WT_CON WT_RB MU_CON MU_RB
> row1       839   180    477   187
> 
> 
> head(counts/c(2,3,4,5))
>               WT_CON    WT_RB    MU_CON    MU_RB
> row1      419.50000  45.0000  238.5000  46.7500
I tried this

df <- data.frame(a=runif(10),b=runif(10),c=runif(10))
scal <- c(2,3,4)
> df
            a          b          c
1  0.47661685 0.73457617 0.90045279
2  0.06916502 0.76374600 0.07630196
3  0.17029174 0.29450289 0.07416969
4  0.03126839 0.09864740 0.08230353
5  0.23713816 0.06342224 0.91241698
6  0.21970595 0.86890690 0.47316101
7  0.46380324 0.26142304 0.87823277
8  0.81256517 0.76097474 0.98956553
9  0.74425369 0.29228545 0.27496707
10 0.65425285 0.40166967 0.12231213
> df/scal
            a          b          c
1  0.23830843 0.24485872 0.22511320
2  0.02305501 0.19093650 0.03815098
3  0.04257293 0.14725144 0.02472323
4  0.01563419 0.03288247 0.02057588
5  0.07904605 0.01585556 0.45620849
6  0.05492649 0.43445345 0.15772034
7  0.23190162 0.08714101 0.21955819
8  0.27085506 0.19024369 0.49478276
9  0.18606342 0.14614273 0.09165569
10 0.32712642 0.13388989 0.03057803

Checking:
> df[4,]/scal
           a          b          c
4 0.01563419 0.03288247 0.02057588


This is what you want guessing from your description.
You haven't given us an example with desired output.

Berend