How to simplify handling with nested ifelse() structures in base R?

Question

I\'m facing nested ifelse() structures:

df1$var <- ifelse(x < a, u, ifelse(x < b, v, ifelse(x < c, w, ...)))

whereby t

Answer 1

Since you insist on base R, here are two possibilities:

Define a mapping data.frame:

# Define mapping
map <- cbind.data.frame(
    x = c(1, 2, 3, 4, NA),
    y = c("s", "t", "u", "v", "w"));

Method 1: match entries from map to df1.

# match entries
df1$y <- map[match(df1$x, map$x), 2];
df1$y[is.na(df1$y2)] <- "w";

Method 2: Loop through all mappings, and replace using direct indexing:

# for loop
df1$y <- factor("w", levels = map$y);
for (i in 1:nrow(map)) df1$y[df1$x == map$x[i]] <- map$y[i];

Output:

tail(df1);
#    x y
#95  4 v
#96  1 s
#97  4 v
#98  2 t
#99  4 v
#100 1 s

Note, the second method will also work for inequalities.

---

Sample data

set.seed(2017);
df1 <- data.frame(x = rbinom(100, 5, .5))