Dear list,
I am very new to R and have been struggling with extracting data from a netcdf
file. Basically I have read in a file containing vegetation height data
organised in 0.5 degree grid cells spanning the whole globe. Each cell contains
a histogram representing the height distribution and I need to extract a single
value (the mean) from each cell. My data has 720 rows and 240 columns so is
pretty large and I’ve been told for loops should be the most straightforward
way to do this. Sorry the code below is not reproducible but hopefully it
illustrates where I am going wrong.
##The following returns the mean value of a single cell (260,90)
> sum(ht.center.vals*(ht.hist[260,90,]))/sum(ht.hist[260,90,])
##but when I try to translate this to a for loop I get NaN
> mean.height<-NULL
> for(i in 1:nrow(ht.hist)){
+ for(j in 1:ncol(ht.hist)){
+ mean.height<-sum(ht.center.vals*(ht.hist[i,j,]))/sum(ht.hist[i,j,])
+ }
+ }
> mean.height
[1] NaN
Can anyone tell me how I tell R to look at each cell in turn, extract the mean
value and save it in a new array? Clearly I am not doing it correctly!
Many thanks,
Jess
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