Making a frequency table with proportions instead of counts. Preview image from https://twitter.com/lyric_rep/status/1010594530435846144.

*This post has been slightly modified from its original form on woodpeckR.*

How can I convert a frequency table into proportions?

This is a continuation of the data manipulation discussed in the `with()`

post. I had just finished making a table

```
# Load data from GitHub
polygon <- read.csv("https://tinyurl.com/rta6hkbo")
# Two-way table by pool and revetment
with(polygon, table(revetment, pool))
```

```
pool
revetment 4 8 13
0 71 199 103
1 57 53 44
```

What if I want to see this table broken down by *proportion* of polygons, not counts?

The `prop.table()`

function will do this nicely.

```
library(dplyr)
prop <- with(polygon, table(revetment, pool)) %>%
prop.table()
prop
```

```
pool
revetment 4 8 13
0 0.13472486 0.37760911 0.19544592
1 0.10815939 0.10056926 0.08349146
```

By default, the proportions are calculated over the entire table. So each cell represents the proportion *of all polygons* that are in that pool with that value of revetment. The whole table sums to 1.

If you want proportions across rows or down columns, all you need to do is add the `margin =`

argument.

`margin = 1`

sums across rows. Each row sums to 1. This would answer the question, “What proportion of the polygons [with, or without] revetment are located in each of the three pools?”

```
prop.1 <- with(polygon, table(revetment, pool)) %>%
prop.table(margin = 1)
prop.1
```

```
pool
revetment 4 8 13
0 0.1903485 0.5335121 0.2761394
1 0.3701299 0.3441558 0.2857143
```

`margin = 2`

sums down columns. Each column sums to 1. This would answer the question, "What proportion of the polygons in [pool] have revetment? (or, what proportion don’t have revetment?)

```
prop.2 <- with(polygon, table(revetment, pool)) %>%
prop.table(margin = 2)
prop.2
```

```
pool
revetment 4 8 13
0 0.5546875 0.7896825 0.7006803
1 0.4453125 0.2103175 0.2993197
```

Handy function for creating proportion tables.

If you see mistakes or want to suggest changes, please create an issue on the source repository.

For attribution, please cite this work as

Gahm (2018, July 22). Kaija Gahm: prop.table(). Retrieved from https://kaijagahm.netlify.app/posts/2018-07-22-proptable/

BibTeX citation

@misc{gahm2018prop.table(), author = {Gahm, Kaija}, title = {Kaija Gahm: prop.table()}, url = {https://kaijagahm.netlify.app/posts/2018-07-22-proptable/}, year = {2018} }