mean( ,na.rm=TRUE) still returns NA

Question

I\'m very new to R (moving over from SPSS). I\'m using RStudio on a Mac running Mavericks. Please answer my question in words of 2 syllables as this is my first real attempt a

Answer 1

unfortunately, as.numeric makes an implicit coercion, which leads to wrong answers. don't imply it on factors.

Answer 2

Hello Rnovice unfortunatly there are several errors... Lets resolve them one by one:

> mean(as.numeric(data_Apr_Jun$hold_time,NA.rm=TRUE))
[1] NA

This is because you use na.rm in a wrong manner: it should be

mean(as.numeric(data_Apr_Jun$hold_time),na.rm=TRUE)

1. na.rm is an argument of mean, not of as.numeric (caution with the brackets)
2. is na.rm R is case sensitive

==================================================================================

> data_Apr_Jun$hold_time[data_Apr_Jun$hold_time=="NA"]<-0

R does not allow comparison with NA as i pointed our here: Something weird about returning NAs
What you mean is

data_Apr_Jun$hold_time[which(is.na(data_Apr_Jun$hold_time))] <- 0

One more remark =="NA" is comparing with a string "NA". Try is.na("NA") and is.na(NA) to see the difference.

==================================================================================

colMeans(data_Apr_Jun$hold_time)
Error in colMeans(data_Apr_Jun$hold_time) : 
  'x' must be an array of at least two dimensions

try data_Apr_Jun$hold_time and you will see, that it returns a vector. This is why a colwise mean (computed by colMeans) makes no sence.

Hope the rest is understandable/solveable with these hints. One very importent thing that you already realized:
Use R! you are on the right track!