[R] nested looping functions and dataframes

[Lanna Jin]

Hey All,

So, I am confused how exactly to use nesting loop functions in R to spit out
data frames.  I've managed to create a working function for my data set that
generates a data frame for a given set of Year i and Location j; but how
would I do it for all Years and Locations?

Here is my working function:

test<-function(i,j){
a<-x[which(x$Year==i & x$Location==j),]
b<-as.data.frame(as.matrix(table(a$Species,a$Species)))
c<-b[-which(b$Var1==b$Var2),-3]
c$Year<-i; c$Location<-j
return(c)
}

Where, x is a dataframe that looks like the following:

> head(x,n=20)
   Year Location    Species
66 1998   PIPE_7      ACMI2
67 1998   PIPE_7      AMAR2
68 1998   PIPE_7      AMCA6
69 1998   PIPE_7       ANCY
70 1998   PIPE_7       ASVE
71 1998   PIPE_7       BOCU
72 1998   PIPE_7       CIFL
73 1998   PIPE_7      DAPU5
74 1998   PIPE_7 DICHANTHEL
75 1998   PIPE_7      GABO2
76 1998   PIPE_7      HEHE5
77 1998   PIPE_7       LIAS
78 1998   PIPE_7       LIPY
79 1998   PIPE_7      PAVI2
80 1998   PIPE_7       PHPI
81 1998   PIPE_7      PHVI5
82 1998   PIPE_7       RAPI
83 1998   PIPE_7      SOCA6
84 1998   PIPE_7      VIPE2
85 1998   PIPE_7       ZIAU

and when feeding x into my function "test" with the parameters i = 1998 and
j = "PIPE_7", I get the following dataframe, c:

> head(test(1998,"PIPE_7"),n=20)
         Var1  Var2 Year Location
2       AMAR2 ACMI2 1998   PIPE_7
3       AMCA6 ACMI2 1998   PIPE_7
4        ANCY ACMI2 1998   PIPE_7
5        ASVE ACMI2 1998   PIPE_7
6        BOCU ACMI2 1998   PIPE_7
7        CIFL ACMI2 1998   PIPE_7
8       DAPU5 ACMI2 1998   PIPE_7
9  DICHANTHEL ACMI2 1998   PIPE_7
10      GABO2 ACMI2 1998   PIPE_7
11      HEHE5 ACMI2 1998   PIPE_7
12       LIAS ACMI2 1998   PIPE_7
13       LIPY ACMI2 1998   PIPE_7
14      PAVI2 ACMI2 1998   PIPE_7
15       PHPI ACMI2 1998   PIPE_7
16      PHVI5 ACMI2 1998   PIPE_7
17       RAPI ACMI2 1998   PIPE_7
18      SOCA6 ACMI2 1998   PIPE_7
19      VIPE2 ACMI2 1998   PIPE_7
20       ZIAU ACMI2 1998   PIPE_7
21      ACMI2 AMAR2 1998   PIPE_7


I have searched through the R-help archives for hints, which have not been
successful in answering my question.  As a new user to R and programming
languages, I truly appreciate your help and thank you for your patience. 

Thanks in advance for your response,
Lanna Jin

-----
Lanna Jin

lannajin at gmail.com
510-898-8525
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