Hi,
I imported a shapefile. There is a string field describing the land use. Now I would like to create an integer field which corresponds to the strings of land use. Last time I did it for each land use type separately (= 1 where [landuse] = "trees" etc.) but if there are many different types it's complicated.
Or should I do it external (i.e. with R)?
Thanks, Rolf
I solved it in R:
I exported the table as csv, read it in R, created the index of the strings and outputted the idr_id and index as AVL file. So, I can generate the raster file with ASSIGN from the raster file with idr_id.
BTW: Is there module to generate an adc for an avl file? I often create avl files externally and copy an existing adc file to create the corresponding adc file. But then I must change the entries manually.
Rolf,
Good that you found a solution. In Database Workshop there is an SQL utility that should do what you were looking for, under the Query menu.
No module to create the ADC.
James
I don't think that's possible with one SQL statement.
Idr_id type_as_text
1 tree
2 acre
3 grass
4 tree
5 grass
6 grass
7 acre
8 tree
Result should be:
1 1
2 2
3 3
4 1
5 3
6 3
7 2
8 1
where tree=1, acre=2, grass=3 but with 20 different types.
I think what you would want to do is create a new field and assign new values to that field based on the land cover text field. Should be doable in SQL.
Yes, but I need for each land cover type a SQL statement:
= 1 where landcover = "tree"
= 2 where landcover = "acre"
= 3 where landcover = "grass" etc.
and you have to know which text field values are present (you can do that with a SQL DISTINCT statement)
Or do you know a solution with one statement?
in R:
# reading the csv table
ez <- read.table("ued_zonenplan.csv", header=TRUE, sep=",")
# create number (type) for land covers (Bez)
ez$type <- as.integer(ez$Bez)
range <- c(1,5) # only columns 1 and 5 as output
# write avl file with idr_id and type to re-assign idr_id
write.table(ez[,range],"ued_idr_id_bauzone.avl", row.names=FALSE, col.names=FALSE, sep=" ")
# subset of unique Bez and type (to know which land cover has which number)
bz <- unique(data.frame(ez[,5],ez[,2]))
# write this subset sorted
write.table(bz[order(unique(ez[,5])),],"zone and ID.txt", row.names=FALSE, col.names=FALSE, sep="=")
Regards, Rolf
No, I don't have a solution for you in sql with a simpler statement.
James