在列表R中的数据框的同一列中找到最小值/最大值

Question

I have 323 data.frame s in a list called mrns . In each data.frame , there is a variable called raw.Systolic . What I need to do is find the minimum/maximum raw.Systolic among ALL 323 data.frame s. I can output the minima for each data.frame , but that's not what I need.

The closest I've gotten so far is outputting the list of minima for each file and trying to find a way to find the minima of that output, but I don't know how.

This is what I have so far:

for (i in 1:323) {
  print(min(mrns[[i]]$raw.Systolic, na.rm=TRUE))
}

Which outputs:

[1] 86
[1] 109
[1] 114
[1] 104
[1] 115
...etc until 323 maximums are listed

When I do:

for (i in 1:323) {
  mins <- min(mrns[[i]]$raw.Systolic, na.rm=TRUE)
}

I get:

> mins
[1] 129

Does anyone have any suggestions?

Answer 1

尝试，

min(unlist(lapply(mrns, function(x) min(x$raw.Systolic, na.rm=T))))

Answer 2

We can do this with:

#minima:
do.call("min",sapply(mrns,getElement,name="raw.Systolic"))

#ranges
do.call("range",sapply(mrns,getElement,name="raw.Systolic"))

#NA-proof
do.call("min",c(sapply(mrns,getElement,name="raw.Systolic"),na.rm=T))

Note that getElement is just the extraction operator $ in function form, ie x$y is the same as getElement(object=x,name="y") .

If you know that all the elements of mrns have the same number of rows, just use min(sapply(...)) instead.

Since sapply is likely to return a list given each element of mrns likely has a different number of rows, we use do.call with allows us to pass a list to min and range .