Trying to Write a For Loop that finds "TRUE" in rows

Question

I'm just trying to run a for loop that identifies which row numbers register as TRUE and prints it in the console.

 Holidays <- c("TRUE", "TRUE", "FALSE", "TRUE")


 newvector <- for (i in 1:length(Holidays))
         {
             if (i == TRUE)
               print(i)
    }

What programming language is this? `boolean` is not a programming language. — tadman, Mar 07 '18 at 18:14
That's better. It's not necessary to tag it in the title, just the tags themselves. That way people can find it and answer it. — tadman, Mar 07 '18 at 18:16
Don't assign your `for` loop, it doesn't return anything. Delete `newvector <-` and your code will print the values. — Gregor Thomas, Mar 07 '18 at 18:18
Also note that the character string `"TRUE"` is different from the boolean value `TRUE`. If your input is `Holidays <- c(TRUE, TRUE, FALSE, TRUE)`, then that is good. And you can just do `which(Holidays)`. — Gregor Thomas, Mar 07 '18 at 18:20
If I remove the variables it prints [1] 1, which isn't correct? — hmnoidk, Mar 07 '18 at 18:21
Oh, also you should be testing if `Holidays[i] == TRUE` - `i` is just a number. — Gregor Thomas, Mar 07 '18 at 18:22
you are looping through integers 1, 2, 3, 4, 5... so your logical has to evaluate at `Holiday[i] == "TRUE` instead of `i==TRUE` — Felipe Alvarenga, Mar 07 '18 at 18:22

Felipe Alvarenga · Answer 1 · 2018-03-08T19:49:46.060

4

If you want to store which rows are TRUE preallocate an empty vector and bind it in the loop.

If you really have TRUE and FALSE as strings, do the following

Holidays <- c("TRUE", "TRUE", "FALSE", "TRUE")
store = c()

for (i in 1:length(Holidays)){
             if (Holidays[i] == "TRUE") # here you want to see whether the element inside Holiday is equals "TRUE"
              store = c(store, i) # store vector you give you which rows are "TRUE"
    }

However, if you have actual logical entries in Holidays, then the correct syntax should be

Holidays <- c(TRUE, TRUE, FALSE, TRUE)
store = c()

for (i in 1:length(Holidays)){
             if (Holidays[i] == TRUE)
              store = c(store, i)
    }

However, as @Badger mentioned, there is no need to loop here. You can easily get the indices using which

store = which(Holidays %in% TRUE)

edited Mar 08 '18 at 19:49

answered Mar 07 '18 at 18:19

Felipe Alvarenga

2,572
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Best answer so far - to complete it you should also mention the difference between `TRUE` and `"TRUE"`. – Gregor Thomas Mar 07 '18 at 18:23
sure, I just supposed he had actual strings, updating answer – Felipe Alvarenga Mar 07 '18 at 18:23
Functionally it answers the question, but the question is still why use a loop at all? – Badger Mar 07 '18 at 23:12

score 2 · Answer 2 · answered Mar 07 '18 at 18:26

2

So using this question as a guide, the command below will get a vector of index numbers from the Holidays vector that match "TRUE":

true_indexes = which(Holidays %in% "TRUE")
print(true_indexes)

answered Mar 07 '18 at 18:26

Tom Cooper

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Another way: print(which(Holidays == T)) – YOLO Mar 07 '18 at 18:56

kgolyaev · Answer 3 · 2018-03-07T22:35:17.117

1

EDIT Please disregard my answer, it is not correct, as it had been pointed out to me.

===========================================================================

Your problem is that you store TRUE and FALSE as strings, not as booleans.

Instead of

Holidays <- c("TRUE", "TRUE", "FALSE", "TRUE")

You should have:

Holidays <- c(TRUE, TRUE, FALSE, TRUE)

The rest of your code should work.

edited Mar 07 '18 at 22:35

answered Mar 07 '18 at 18:20

kgolyaev

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That's not a problem. Check 'TRUE' == TRUE – YOLO Mar 07 '18 at 18:56
I guess you're right, @ManishSaraswat, I stand corrected. Learned something new today :) – kgolyaev Mar 07 '18 at 22:34

score 1 · Answer 4 · answered Mar 07 '18 at 20:55

1

Why do you want to do it with a for loop ? If you change cour mind you can do it with which. Works with non boolean, too

newvector <-which(Holidays == "TRUE")

answered Mar 07 '18 at 20:55

Grigorij Abramov

51
6

Thanks. I am a newbie and I was just very stubborn about pulling off a for loop, haha. For my own amusement. – hmnoidk Mar 08 '18 at 21:53

Trying to Write a For Loop that finds "TRUE" in rows

4 Answers4