[R] Apply Function to Columns

[Sarah]

Hello List, 

I have a database which consist of 912 plots. For each plot, I have the presence/absence information of 260 species of plants and also 5 different environmental variables (ddeg, mind, srad, slp, topo).

The dataframe looks like this: 

  Plot_Number        X       	 Y 	ddeg mind   srad slp topo Galium_mollugo Gentiana_nivalis
1        1 		557747.6 149726.8 2598 -625 236363   8  176              0                0
2        2 		572499.4 145503.5 2178 -176 161970  14 -137              0                0
3        3 		579100.4 151800.4 1208  632 267572  33  129              0                0
4        4 		581301.7 150300.1 1645   83 246633  15  -70              0                0
5        5 		579838.7 124770.9 1102 1637 158300   2 -231              0                0
6        6 		577011.1 121328.6  731 2223 180286  41   70              0                0

Now, what I wanted to do is to calculate spatial autocorrelation of each environmental variable for each species, but only for the plots where the species is present. 

I will use the correlog function of the package ncf (doesn’t really matter). The correlog function work with an argument X which is the longitude, an argument Y which is the latitude and an argument Z which is the variable you want to test for autocorrelation (in my case, the different environmental variables). 

So, for the first species I have the following script:

ddeg.correlog.9<-correlog(plant[plant[,9]=="1", 2], plant[plant[,9]=="1", 3], plant[plant[,9]=="1", 4]) 

X = plant[plant[,9]=="1", 2] —>  only the X coordinate where my species 9 is present
Y = plant[plant[,9]=="1", 3] —>  only the Y coordinate where my species 9 is present
Z = plant[plant[,9]=="1", 4] —>  only the value of the environmental variable where my species 9 is present

plant: dataframe
9: column corresponding to the first species
2: column corresponding to the X coordinate
3: column correspondind to the Y coordinate
4: column corresponding to the first environmental variable

So my question is: how do I repeat this script for every species (basically, I just have to change the number « 9 » into 10, 11 and so on) ?

I try to write a function but I’m new in R and didn’t manage to do it. I was also considering to use the function « lapply », but I don’t think I can use it in this case, isn’t it? 

Thank you very much for your help !

Sarah