Converting string to numeric

Question

I've imported a test file and tried to make a histogram

pichman <- read.csv(file="picman.txt", header=TRUE, sep="/t")   
hist <- as.numeric(pichman$WS)    

However, I get different numbers from values in my dataset. Originally I thought that this because I had text, so I deleted the text:

table(pichman$WS)    
ws <- pichman$WS[pichman$WS!="Down" & pichman$WS!="NoData"]    

However, I am still getting very high numbers does anyone have an idea?

Answer 1

I suspect you are having a problem with factors. For example,

> x = factor(4:8)
> x
[1] 4 5 6 7 8
Levels: 4 5 6 7 8
> as.numeric(x)
[1] 1 2 3 4 5
> as.numeric(as.character(x))
[1] 4 5 6 7 8

Some comments:

• You mention that your vector contains the characters "Down" and "NoData". What do expect/want as.numeric to do with these values?
• In read.csv, try using the argument stringsAsFactors=FALSE
• Are you sure it's sep="/t and not sep="\t"
• Use the command head(pitchman) to check the first fews rows of your data
• Also, it's very tricky to guess what your problem is when you don't provide data. A minimal working example is always preferable. For example, I can't run the command pichman <- read.csv(file="picman.txt", header=TRUE, sep="/t") since I don't have access to the data set.