Summary statistics using ddply
I like to write a function using ddply
that outputs the summary statistics based on the name of two columns of data.frame
mat
.
mat
is a bigdata.frame
with the name of columns"metric", "length", "species", "tree", ...,"index"
index
is factor with 2 levels"Short", "Long"
"metric", "length", "species", "tree"
and others are all continuous variables
Function:
summary1 <- function(arg1,arg2) {
...
ss <- ddply(mat, .(index), function(X) data.frame(
arg1 = as.list(summary(X$arg1)),
arg2 = as.list(summary(X$arg2)),
.parallel = FALSE)
ss
}
I expect the output to look like this after calling summary1("metric","length")
Short metric.Min. metric.1st.Qu. metric.Median metric.Mean metric.3rd.Qu. metric.Max. length.Min. length.1st.Qu. length
.Median length.Mean length.3rd.Qu. length.Max.
....
Long metric.Min. metric.1st.Qu. metric.Median metric.Mean metric.3rd.Qu. metr开发者_Go百科ic.Max. length.Min. length.1st.Qu. length
.Median length.Mean length.3rd.Qu. length.Max.
....
At the moment the function does not produce the desired output? What modification should be made here?
Thanks for your help.
Here is a toy example
mat <- data.frame(
metric = rpois(10,10), length = rpois(10,10), species = rpois(10,10),
tree = rpois(10,10), index = c(rep("Short",5),rep("Long",5))
)
As Nick wrote in his answer you can't use $
to reference variable passed as character name. When you wrote X$arg1
then R
search for column named "arg1"
in data.frame
X
. You can reference to it either by X[,arg1]
or X[[arg1]]
.
And if you want nicely named output I propose below solution:
summary1 <- function(arg1, arg2) {
ss <- ddply(mat, .(index), function(X) data.frame(
setNames(
list(as.list(summary(X[[arg1]])), as.list(summary(X[[arg2]]))),
c(arg1,arg2)
)), .parallel = FALSE)
ss
}
summary1("metric","length")
Output for toy data is:
index metric.Min. metric.1st.Qu. metric.Median metric.Mean metric.3rd.Qu.
1 Long 5 7 10 8.6 10
2 Short 7 7 9 8.8 10
metric.Max. length.Min. length.1st.Qu. length.Median length.Mean length.3rd.Qu.
1 11 9 10 11 10.8 12
2 11 4 9 9 9.0 11
length.Max.
1 12
2 12
Is this more like what you want?
summary1 <- function(arg1,arg2) {
ss <- ddply(mat, .(index), function(X){ data.frame(
arg1 = as.list(summary(X[,arg1])),
arg2 = as.list(summary(X[,arg2])),
.parallel = FALSE)})
ss
}
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