Dynamic Format Matching Strings in R
I want to check if there is no column for the header of the input data frame. The problem occurs when I use fread(filename)
to change the missing header to the default name "V + Number of column" (ex: V1 for the first column, V2, etc.). I've read the documentation for this feature and can't seem to change this default for headers. So with that in mind, I want all the containing columns to V + number
be missing from the headers. It will be very helpful if someone explains how to do something like this:
if(string == (V1, V2, ... VN)){ do something }
Similar to comparison if String is 'V' plus an integer.
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you can get all Vx column values using str_extract from the stringr package. I think.
library(stringr)
str_extract(colnames(myDataFrame), "V\\d*")
Example:
dt <- data.frame("aaaa" = c(1:5), "V2" = c(6:10), "V3123" = c(11:15), "V455" = c(16:20))
str_extract(colnames(dt), "V\\d*")
"NA" "V2" "V3123" "V455"
Then you can do what you need with the column names
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Like this? I don't know exactly what you want to do with the missing column names; if you want to replace them with spaces or write their positions, adjust the print statements to make a vector with, for example, everything i
where It missing
.
x <- data.frame(A=1,B=2,V3=3,V4=4,C=5)
z <- names(x)
for(i in 1:length(z)){
if(z[i]==paste0("V", i)){
print("It missing")
} else {
print("Not missing")
}
}
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