如何检查函数在R中期望的最少参数个数？
要找到函数在R中使用时期望的最少数量的参数，可以借助以下语法来完成：length（formals（“function_name”））。例如，要查找dplyr软件包的mutate函数期望的参数数量，可以使用命令length（formals(mutate)）计算出来，但是我们需要确保已加载该软件包。
例子
library(ggplot2) length(formals(ggplot))输出结果
[1] 4 length(formals(boxplot)) [1] 2 length(formals(qnorm)) [1] 5 length(formals(rnorm)) [1] 3 length(formals(rpois)) [1] 2 length(formals(runif)) [1] 3 length(formals(punif)) [1] 5 length(formals(plot)) [1] 3 length(formals(pbinom)) [1] 5 length(formals(qbinom)) [1] 5 length(formals(hist)) [1] 2 length(formals(data)) [1] 7 length(formals(matrix)) [1] 5 length(formals(list)) [1] 0 length(formals(data.frame)) [1] 6 length(formals(paste)) [1] 4 length(formals(gsub)) [1] 7 length(formals(factor)) [1] 6 length(formals(cut)) [1] 2 length(formals(t.test)) [1] 2 length(formals(lm)) [1] 14 length(formals(glm)) [1] 18 length(formals(prop.test)) [1] 6 length(formals(pairwise.t.test)) [1] 7 length(formals(aov)) [1] 6 length(formals(dunif)) [1] 4 length(formals(dpois)) [1] 3 length(formals(dnorm)) [1] 4 length(formals(cbind)) [1] 2 length(formals(rbind)) [1] 2 length(formals(cor)) [1] 4 length(formals(cor.test)) [1] 2 length(formals(mean)) [1] 2 length(formals(sum)) [1] 0 length(formals(median)) [1] 3 length(formals(quantile)) [1] 2 length(formals(rank)) [1] 3 length(formals(var)) [1] 4 length(formals(sd)) [1] 2 length(formals(round)) [1] 0