Using If Else Conditions on Vectors

Using if/ifelse statement with vector conditions in R

You can also do a normal if statement, since it returns a value:

my_result = if(all(Vector1 == c(T,T,T))) {"Combo1"} else {"Combo2"}

The ifelse function is made for vectorized conditional statements.

By using the standard if statement, you remove potential ambiguity/misinterpretation because the standard if only evaluates one condition.

Vectorized IF statement in R?

x <- seq(0.1,10,0.1)

> x
  [1]  0.1  0.2  0.3  0.4  0.5  0.6  0.7  0.8  0.9  1.0  1.1  1.2  1.3  1.4  1.5
 [16]  1.6  1.7  1.8  1.9  2.0  2.1  2.2  2.3  2.4  2.5  2.6  2.7  2.8  2.9  3.0
 [31]  3.1  3.2  3.3  3.4  3.5  3.6  3.7  3.8  3.9  4.0  4.1  4.2  4.3  4.4  4.5
 [46]  4.6  4.7  4.8  4.9  5.0  5.1  5.2  5.3  5.4  5.5  5.6  5.7  5.8  5.9  6.0
 [61]  6.1  6.2  6.3  6.4  6.5  6.6  6.7  6.8  6.9  7.0  7.1  7.2  7.3  7.4  7.5
 [76]  7.6  7.7  7.8  7.9  8.0  8.1  8.2  8.3  8.4  8.5  8.6  8.7  8.8  8.9  9.0
 [91]  9.1  9.2  9.3  9.4  9.5  9.6  9.7  9.8  9.9 10.0

> ifelse(x < 5, 1, 2)
  [1] 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
 [38] 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2
 [75] 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2

How to write a if and else statement for a vector?

You might use std::find:

std::vector<int> myvec {1,2,3,4,5};
if (std::find(myvec.begin(), myvec.end(), 1) != myvec.end()) {
    cout << "yes it is there" << endl;
}

R - vectorized if for multiple conditions

How about this?

It's the same function as above, but without the explicit if and else?

> Teff=seq(30,40,1)
> hsa<- 1*(Teff<Tcr) + (1 - (Teff - Tcr)/(Tlim - Tcr))*(Teff >= Tcr & Teff < Tlim)
> hsa
 [1] 1.0000000 1.0000000 1.0000000 1.0000000 0.8571429 0.7142857 0.5714286 0.4285714 0.2857143 0.1428571 0.0000000

** Note that you can add + 0*(Teff>=Tlim) in the end, but it wouldn't change anything, because the assigned value would be 0 anyways.

If you really want to use ifelse, then you have to nest them, so it should be something like this:

> hsa<- ifelse(Teff<Tcr, 1,
               ifelse(Teff >= Tcr & Teff < Tlim, 
               (1 - (Teff - Tcr)/(Tlim - Tcr)), 0))
> hsa
     [1] 1.0000000 1.0000000 1.0000000 1.0000000 0.8571429 0.7142857 0.5714286 0.4285714 0.2857143 0.1428571 0.0000000

ifelse function on a vector

ifelse is vectorized and its result is as long as the test argument. all(is.na(vect)) is always just length one, hence the result. a regular if/else clause is fine here.

vect <- c("NA_NA", "14_mter", "78_ONHY")

if (all(is.na(vect))) {
  out <- vect 
} else {
  out <- vect[vect != "NA_NA"]
}
out
#> [1] "14_mter" "78_ONHY"

additional note: no need for the which() here

In R how to use an ifelse() with a vector or dataframe for classification

There is a dplyr way to do this.

library(dplyr)
sp_data %>%
  inner_join(size_data, by = c("X1" = "S1")) %>%
  mutate(X4 = case_when(X2 >= S2 ~ "above",
                        TRUE ~ "below")) %>%
select(-S2)
     X1 X2    X4
1 fish1 20 below
2 fish1 30 above
3 fish2 32 above
4 fish2 21 below
5 fish3 50 above

How to search in vector with If and else statement

You're trying too hard, simply

if (myvec[0] == 1)

For extra security you could add a check that the vector is not empty

if (!myvec.empty() && myvec[0] == 1)

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