# [R] use ggplot in a function to which a column name is given

From: jiho <jo.irisson_at_gmail.com>
Date: Thu, 13 Dec 2007 10:45:32 +0100

ggplot makes it very easy to plot things given their names when you use it interactively (and therefore can provide the names of the columns).

qplot(x,foo,data=A) where A has columns (x,y,foo,bar) for example

but I would like to use this from inside a function to which the name of the column is given. I cannot find an elegant way to make this work. Here are my attempts:

```#------------------------------------------------------------

```

library(ggplot2)

A = data.frame(x=rep(1:10,10), y=rep(1:10,each=10), u=runif(100), v=rnorm(100))

# goal: extract values for y<=5 and plot them, either for u or v

foo1 <- function(uv="u")
{

# solution 1: do not use the data argument at all
# (forces the use of qplot, could be more elegant)

```	B = A[A\$y<=5,]
qplot(B\$x, B\$y, fill=B[[uv]], geom="tile")
```
}

foo2 <- function(uv="u")
{

# solution 2: extract and rename the colums, then use the data argument
# (enables ggplot but could be shorter)

```	B = A[A\$y<=5,c("x","y",uv)]
names(B) = "value"

# rem: cannot use rename since rename(B,c(uv="value")) would not work

qplot(x, y, fill=value, data=B, geom="tile")

# or
# ggplot(B,aes(x=x,y=y,fill=value)) + geom_tile()

```
}

foo3 <- function(uv="u")
{

# solution 3: use the data argument and perform the extraction
directly in it

```	#	(elegant and powerful but can't make it work)
ggplot(A[A\$y<=5,c("x","y",uv)],aes(x=x,y=y,fill=???)) + geom_tile()

# or
ggplot(A[A\$y<=5,],aes(x=x,y=y,fill=???)) + geom_tile()

# or ...

```

}
```print(foo1("u"))
print(foo1("v"))
print(foo2("u"))
print(foo3("u"))

#------------------------------------------------------------

```

Any help in making foo3 work would be appreciated. Thanks in advance for your expertise.

JiHO

```---
http://jo.irisson.free.fr/

______________________________________________
R-help_at_r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help