在 R 中跨列应用函数列表以填写表格

Question

I have a dataframe in R, let's call it df , which I would like to analyse in terms of mean, median, standard deviation, IQR etc column-wise. I have prepared succinct functions (where it's not just mean or sd ) which can take a vector as input and output, say, the IQR or coefficient of variance. Now, if I want to apply any of these across the attributes (columns), I could use IQRs <- apply(df,2,IQR) for example.

My question is, how can I apply multiple of these functions together (really, I want to chain them all together), so as to fill in a table where there will be one column for the attributes and then one column per function (ie Means will be one column, IQRs will be one column), and the different attributes of the data-frame (which were columns in df ) will be rows of this table (listed in the first column)?

Answer 1

Suppose your data looked like this:

set.seed(69)
df <- data.frame(A = rnorm(5), B = rnorm(5), C = rnorm(5))

And your function names were like this:

funcs <- c("mean", "median", "sd", "var", "min", "max")

Then you can use an apply inside an lapply like this:

as.data.frame(setNames(lapply(funcs, function(f) apply(df, 2, as.name(f))), funcs))
#>        mean     median        sd       var       min       max
#> A -0.3546864 -0.3348139 0.5948611 0.3538597 -0.949889 0.3743156
#> B -0.2016318 -0.9039467 1.4092795 1.9860687 -1.571073 1.4440935
#> C -0.3537707 -0.1691765 0.7955558 0.6329090 -1.311374 0.4149940

Answer 2

You can use tidyr::gather and dplyr::summarize :

# Toy data
df <- data.frame(x = 1:10, y = 11:20)

# Libs
library(tidyverse)

# Code
df %>% 
    gather(var, val) %>% 
    group_by(var) %>% 
    summarize(med = median(val), mean = mean(val), iqr = IQR(val))

Output:

# A tibble: 2 x 4
  var     med  mean   iqr
  <chr> <dbl> <dbl> <dbl>
1 x       5.5   5.5   4.5
2 y      15.5  15.5   4.5