# Re: [R] Convert a presence/ absence matrix to a list of presence only

From: jim holtman <jholtman_at_gmail.com>
Date: Fri, 22 Apr 2011 22:56:40 -0400

try this; added an extra row so that the lengths would not be even:

```+ spcs1   1       1       0
+ spcs2   1       0       1
+ spcs3   0       1       1
+ spcs4   0       0       1"), header = TRUE)
```

> closeAllConnections()
> x
```      spl_A spl_B spl_C
spcs1     1     1     0
spcs2     1     0     1
spcs3     0     1     1
spcs4     0     0     1
```

>
> # get maximum in any column so we can pad out the lengths
> maxLen <- max(colSums(x))
>
>
> combine <- lapply(x, function(.col){
```+     sp <- row.names(x)[.col == 1]
+     c(sp, rep("", maxLen - length(sp)))
+ })
```

>
> do.call(cbind, combine)

spl_A spl_B spl_C

```[1,] "spcs1" "spcs1" "spcs2"
[2,] "spcs2" "spcs3" "spcs3"
[3,] ""      ""      "spcs4"
```

>

On Fri, Apr 22, 2011 at 2:10 PM, antu <ananta.acharya_at_gmail.com> wrote:
> (http://r.789695.n4.nabble.com/how-to-combine-presence-only-data-sets-to-one-presence-absence-table-td830140.html
> ) covered the need for making present list list to a matrix,
>
> Now, I ran into an opposite problem. I have a data matrix with 0, 1 on them,
> what I need now is list of presence only for each column name
>
> ie, this is what I have
>
>        spl_A   spl_B   spl_C
> spcs1   1       1       0
> spcs2   1       0       1
> spcs3   0       1       1
>
>
> this is what I need
>
> spl_A     spl_B spl_C
> spcs1  spcs1    spcs2
> spcs2    spcs3  spcs3
>
>
>
> Thank you
>
> --
> View this message in context: http://r.789695.n4.nabble.com/Convert-a-presence-absence-matrix-to-a-list-of-presence-only-tp3468479p3468479.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help_at_r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> and provide commented, minimal, self-contained, reproducible code.
>

```--
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?

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