对具有相似名称的变量执行相似计算的函数 [英] Function to perform similar calculations on variables with similar names

问题描述

我有一个看起来像这样的数据框

I have a dataframe which looks like this

var1<-c(150,20,30)
var2<-c(20,30,40)
x<-c(2.5,4.5,7.5)
s_var1<-c(0,0,0)
s_var2<-c(0,0,0)

data<-data.frame(var1, var2, x, s_var1, s_var2)

可能有一大堆var"列 - var1、var2....var'n'.与 s_var1、s_var2..... 等相同.

There could be a whole bunch of 'var' columns - var1, var2....var'n'. Same with s_var1, s_var2.....etc.

我想编写一个函数，在引用 'var' 列和 'x' 列的同时对 's_var' 列进行计算.

I want to write a function which does calculations on the 's_var' columns while referencing the 'var' columns and the 'x' column.

例如:如果有 2 个 'var' 列

For example: if there are 2 'var' columns

n_var<-c(1,2)

for (i in n_var)
{
if (x > 2.5) { s_var[i] = var[i] } else {s_var[i] = 2*var[i]}
}

有什么建议吗?我正在努力将列表中的数字作为后缀传递给引用列名...

Any suggestions? I am struggling to pass the numbers in the list as suffixes to reference column names...

推荐答案

使用grep查找var和s_var的列索引列并定义依赖于 x 的 multiplier.最后应用乘数.请注意，乘数将被循环使用以乘以 data[var_cols] 中的每一列.

Use grep to find the column indexes of the var and s_var columns and define a multiplier which depends on x. Finally apply the multiplier. Note that the multiplier will be recycled to multiply each of the columns in data[var_cols].

fun <- function(data) {
  var_cols <- grep("^var", names(data))
  s_var_cols <- grep("^s_var", names(data))
  multiplier <- (x > 2.5) + 1
  data[s_var_cols] <- multiplier * data[var_cols]  ##
  data
}

fun(data)

给予:

  var1 var2   x s_var1 s_var2
1  150   20 2.5    150     20
2   20   30 4.5     40     60
3   30   40 7.5     60     80

上面的## 行也可以这样写，这里不是真的需要，但如果计算更复杂，则可能需要使用 lapply 或 mapply.

The ## line above could also be written like this, which is not really needed here but if the calculation were more complex then using lapply or mapply might be needed.

data[s_var_cols] <- lapply(data[var_cols], `*`, multiplier)

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