Store and use operators on command

Question

How (and can) I use different operators on command in if and else function?

x <- as.numeric(c(1,1,4,5,6,7,8))

if(mean(x) < 3){operator.is <- <}else{operator.is <- >}

sub <- subset(x, x operator.is 2)

#expected results
sub
[1] 3 4 5 6 7 8

I want to store the operator in "operator.is", based on the if statement. Yet, I do not seem to be able to store an operator and use it in the subset function. Later in want to use this operator to subset. Without this I will need to copy and past the whole code just to use the other operator. Is there any elegant and simple way to solve this?

Thanks in advance

So you want to subset `x` according to `mean(x) < 3` ? Where does `3` come from in your expected output? Also, no need for `as.numeric` in your first line. — markus, May 14 '19 at 07:51
Any operator is just a function. `operator.is <- \`<\`; operator.is(3,4)` — Oliver, May 14 '19 at 07:51
You might [use `switch`](https://stackoverflow.com/questions/10393508/how-to-use-the-switch-statement-in-r-functions) — markus, May 14 '19 at 08:07

score 0 · Accepted Answer · answered May 14 '19 at 07:50

0

operators can be assigned with the % sign:

`%op%` = `>`

vector <- c(1:10)

vector2 <- subset(vector, vector %op% 5)

In your case:

x <- as.numeric(c(1,1,4,5,6,7,8))

if(mean(x) < 3){`%operator.is%` <- `<`}else{`%operator.is%` <- `>`}

sub <- subset(x, x %operator.is% 2)

answered May 14 '19 at 07:50

Sven

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Yes, perfect, thank you. Easy and simple. Found the answer somewhere else as well. – May 14 '19 at 11:45

Bruce Schardt · Answer 2 · 2019-05-14T08:00:23.340

x <- as.numeric(c(1,1,4,5,6,7,8))

if(mean(x) < 3){`%my_op%` <- `<`}else{`%my_op%` <- `>`}

sub <- subset(x, x %my_op% 2)
sub
##[1] 4 5 6 7 8

"Things to remember while defining your own infix operators are that they must start and end with %. Surround it with back tick (`) in the function definition and escape any special symbols."

from https://www.datamentor.io/r-programming/infix-operator/

better to follow the lead of @Oliver and just

x <- as.numeric(c(1,1,4,5,6,7,8))

if(mean(x) < 3){operator.is <- `<`}else{operator.is <- `>`}

sub <- subset(x, operator.is(x,2))
sub
##[1] 4 5 6 7 8

Store and use operators on command

2 Answers2