I have a data frame with several columns. rows have names.
I want to calculate some value for each row (col1/col2) and create a new data frame with the original row names. If I just do something like data$col1/data$col2 I get a vector with the results but lose the row names.
i know it's very basic but I'm quite new to R.
It would help to read ?"[.data.frame" to understand what's going on. Specifically:
Note that there is no ‘data.frame’ method for ‘$’, so ‘x$name’ uses the default method which treats ‘x’ as a list.
You will see that the object's names are lost if you convert a data.frame to a list (using Joris' example data):
> as.list(Data)
$col1
[1] -0.2179939 -2.6050843 1.6980104 -0.9712305 1.6953474 0.4422874
[7] -0.5012775 0.2073210 1.0453705 -0.2883248
$col2
[1] -1.3623349 0.4535634 0.3502413 -0.1521901 -0.1032828 -0.9296857
[7] 1.4608866 1.1377755 0.2424622 -0.7814709
My suggestion would be to avoid using $ if you want to keep row names. Use this instead:
> Data["col1"]/Data["col2"]
col1
a 0.1600149
b -5.7435947
c 4.8481157
d 6.3816918
e -16.4146120
f -0.4757387
g -0.3431324
h 0.1822161
i 4.3114785
j 0.3689514