[R] merge function to combine two tables

[Michael Eisenring]

Dear R-help members

I would be grateful if anyone could help me with the following problem:

I would like to combine two matrices (Schmitt_15 and Schmitt_16, they are attached) which have a  species presence/absence x sampling plot structure. The aim would be to have in the end only one matrix which shows all existing species and their presence/absence on all the different plots.
To do this I used the "merge" function in R. 
The problem is that my matrix in the end shows only 12 species (but there are in total about 100!). I don't know why.

I used the following commands:


Schmitt_15
Schmitt_16
output<-merge(Schmitt_15,Schmitt_16,by="species")
write.table(ab,file="output.txt",sep=",")

Can anyone help me?
Thank you very much!
Michael
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