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I was using the prcomp function when I received this error
Error in prcomp.default(x, ...) : cannot rescale a constant/zero column to unit variance I know I can scan my data manually but is there any function or command in R that can help me remove these constant variables? I know this is a very simple task, but I have never been across any function that does this.
Thanks,
420
The most easiest way to drop columns is by using subset() function. In the code below, we are telling R to drop variables x and z. The '-' sign indicates dropping variables. Make sure the variable names would NOT be specified in quotes when using subset() function.
We can delete multiple columns in the R dataframe by assigning null values through the list() function.
In R, the easiest way to remove columns from a data frame based on their name is by using the %in% operator. This operator lets you specify the redundant column names and, in combination with the names() function, removes them from the data frame. Alternatively, you can use the subset() function or the dplyr package.
The problem here is that your column variance is equal to zero. You can check which column of a data frame is constant this way, for example :
df <- data.frame(x=1:5, y=rep(1,5)) df # x y # 1 1 1 # 2 2 1 # 3 3 1 # 4 4 1 # 5 5 1 # Supply names of columns that have 0 variance names(df[, sapply(df, function(v) var(v, na.rm=TRUE)==0)]) # [1] "y" So if you want to exclude these columns, you can use :
df[,sapply(df, function(v) var(v, na.rm=TRUE)!=0)] EDIT : In fact it is simpler to use apply instead. Something like this :
df[,apply(df, 2, var, na.rm=TRUE) != 0] If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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