[R] Reshape - strange outputs

[Steve Murray]

Dear R Users,

I am using the reshape package to reformat gridded data into column format using the code shown below. However, when I display the resulting object, a single column is fomed (instead of three) and all the latitude values (which should be in either column one or two) are collected at the bottom. Also, the NA values aren't removed, despite this being requested in the code.

Code:


# NetCDF file has been read in and is being processed...

arunoff_1986_temp <- get.var.ncdf(netcdf_1036_temp, "arunoff")


# Assign row and column names

columnnames <- sprintf("%.2f", seq(from = -89.75, to = 89.75, length = 360))
rnames <- sprintf("%.2f", seq(from = -179.75, to = 179.75, length = 720))

colnames(arunoff_1986_temp) <- columnnames
rownames(arunoff_1986_temp) <- rnames


# Melt into columnar format

arunoff_1986$Longitude <- rownames(arunoff_1986)
    # Note: If I do: arunoff_1986$Latitude <- rownames(arunoff_1986)  (i.e. change it to 'Latitude', I get the following: Warning message: In arunoff_1986$Latitude <- rownames(arunoff_1986) : Coercing LHS to a list ), thus proceed using 'Longitude' where no warning is apparent.


arunoff_long_1986 <- melt(arunoff_1986, id.var="Longitude", na.rm=TRUE)


> dim(arunoff_long_1986)
[1] 259560      2

>head(arunoff_long_1986, n=10)  # This displays what looks like one single column, but is in fact two: column entitled "L1" is empty until the end of the file, as shown by the 'tail' command below.
   value L1
1      
2      
3      
4      
5      
6      
7      
8      
9      
10     

> tail(arunoff_long_1986, n=10)
             value       L1
Latitude.351 85.25 Latitude
Latitude.352 85.75 Latitude
Latitude.353 86.25 Latitude
Latitude.354 86.75 Latitude
Latitude.355 87.25 Latitude
Latitude.356 87.75 Latitude
Latitude.357 88.25 Latitude
Latitude.358 88.75 Latitude
Latitude.359 89.25 Latitude
Latitude.360 89.75 Latitude



I'd be very grateful indeed if anyone is able to offer assistance by way of pointing out what I've done wrong. I've spent a long time working on this and trying various options, but am srill none the wiser! I'm aiming for three columns: Latitude, Longitude, 'value'. 

Many thanks for any help offered,

Steve