Hi Robert,
There is a policy of not doing people's homework for them on the list.
Nevertheless, I would advise you to read up on how to use the
comparison operator (==). Good luck.
Jim
On Tue, Jan 17, 2017 at 7:10 AM, Robert Piliero
<robert.pili...@gmail.com> wrote:
> Hello,
>
> I am working on a Coursera assignment and have combined 332 files into a
> single data frame called "dat". The dataframe has 4 columns,
>
> 1. Date
> 2. Sulfate (numerical values)
> 3. Nitrate (numerical values)
> 4. ID # (numerical values).
>
> Our assignment is to write a function pollutantmean <- function(directory,
> pollutant, ID). whereby we can calculate the mean by inputting the
> pollutant name and ID #.
>
> I have reached the stage of subsetting the date e.g. by ID # 1-10, however
> when I do so and then calculate the mean of this subset I receive the NaN
> message (even though I have instructed R to disregard the "NA"'s).
>
>
> *Beginning Code: *
> getwd()
> read.csv(specdata)
> specdata <- ("C:/Users/rober/specdata")
> list.files(specdata)
> files_full <- list.files(specdata, full.names=TRUE)
> files_full
> dat <- data.frame()
> for (i in 1:332){
> dat <- rbind(dat,read.csv(files_full[i]))
> }
> str(dat)
> mean(dat$sulfate, na.rm=TRUE)
>
> *Code which generated the NaN message. *
> dat1_10 <- dat[which(dat[,ID] ==1:10),]
> mean(dat1_10$sulfate, na.rm=TRUE)
>
> Am I making a mistake in subsetting the rows with ID's 1:10? Any advice
> would be appreciated.
>
> Thank you,
>
> Robert
>
> Robert J. Piliero
>
> Cell: (617) 283 1020
> 38 Linnaean St. #6
> Cambridge, MA, 02138
> USA
>
> [[alternative HTML version deleted]]
>
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