在R中，计算字符串向量中的表达式 [英] In R, evaluate expressions within vector of strings

问题描述

我希望评估一个包含算术表达式-"1 + 2"，"5 * 6"等的字符串向量

I wish to evaluate a vector of strings containing arithmetic expressions -- "1+2", "5*6", etc.

我知道我可以将单个字符串解析为一个表达式，然后像eval(parse(text="1+2"))中那样对其求值.

I know that I can parse a single string into an expression and then evaluate it as in eval(parse(text="1+2")).

但是，我宁愿不使用for循环来评估向量.

However, I would prefer to evaluate the vector without using a for loop.

foo <- c("1+2","3+4","5*6","7/8") # I want to evaluate this and return c(3,7,30,0.875)
eval(parse(text=foo[1])) # correctly returns 3, so how do I vectorize the evaluation?
eval(sapply(foo, function(x) parse(text=x))) # wrong! evaluates only last element

推荐答案

只需应用整个功能.

sapply(foo, function(x) eval(parse(text=x)))

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