Say I have a data matrix like this one:
> data(mtcars)
> my_mat <- as.matrix(mtcars[,1:7])
> head(my_mat)
mpg cyl disp hp drat wt qsec
Mazda RX4 21.0 6 160 110 3.90 2.620 16.46
Mazda RX4 Wag 21.0 6 160 110 3.90 2.875 17.02
Datsun 710 22.8 4 108 93 3.85 2.320 18.61
Hornet 4 Drive 21.4 6 258 110 3.08 3.215 19.44
Hornet Sportabout 18.7 8 360 175 3.15 3.440 17.02
Valiant 18.1 6 225 105 2.76 3.460 20.22
... and a thresholds data frame like the following one, with threshold values for some of the columns in the matrix above:
> threshold_df <- data.frame(marker=colnames(my_mat)[c(3,4,6)], threshold=apply(my_mat[,c(3,4,6)], 2, quantile, 0.75))
> threshold_df
marker threshold
disp disp 326.00
hp hp 180.00
wt wt 3.61
With this information, I want to end up with a matrix of 0s and 1s, identical to my_mat, where everything is a 0 except for the values of a column which are higher than the threshold for that column.
So far I have the all-0 matrix, but not sure how to populate the 1s based on the above information... Any clue? Thanks!
> zero_mat <- matrix(0, nrow = nrow(my_mat), ncol = ncol(my_mat))
> colnames(zero_mat) <- colnames(my_mat)
> rownames(zero_mat) <- rownames(my_mat)
> head(zero_mat)
mpg cyl disp hp drat wt qsec
Mazda RX4 0 0 0 0 0 0 0
Mazda RX4 Wag 0 0 0 0 0 0 0
Datsun 710 0 0 0 0 0 0 0
Hornet 4 Drive 0 0 0 0 0 0 0
Hornet Sportabout 0 0 0 0 0 0 0
Valiant 0 0 0 0 0 0 0
Another base R option
u <- with(threshold_df, mapply(`>`, as.data.frame(my_mat[, marker]), threshold))
my_mat <- 0 * my_mat
my_mat[, colnames(u)] <- u
gives
> my_mat
mpg cyl disp hp drat wt qsec
Mazda RX4 0 0 0 0 0 0 0
Mazda RX4 Wag 0 0 0 0 0 0 0
Datsun 710 0 0 0 0 0 0 0
Hornet 4 Drive 0 0 0 0 0 0 0
Hornet Sportabout 0 0 1 0 0 0 0
Valiant 0 0 0 0 0 0 0
Duster 360 0 0 1 1 0 0 0
Merc 240D 0 0 0 0 0 0 0
Merc 230 0 0 0 0 0 0 0
Merc 280 0 0 0 0 0 0 0
Merc 280C 0 0 0 0 0 0 0
Merc 450SE 0 0 0 0 0 1 0
Merc 450SL 0 0 0 0 0 1 0
Merc 450SLC 0 0 0 0 0 1 0
Cadillac Fleetwood 0 0 1 1 0 1 0
Lincoln Continental 0 0 1 1 0 1 0
Chrysler Imperial 0 0 1 1 0 1 0
Fiat 128 0 0 0 0 0 0 0
Honda Civic 0 0 0 0 0 0 0
Toyota Corolla 0 0 0 0 0 0 0
Toyota Corona 0 0 0 0 0 0 0
Dodge Challenger 0 0 0 0 0 0 0
AMC Javelin 0 0 0 0 0 0 0
Camaro Z28 0 0 1 1 0 1 0
Pontiac Firebird 0 0 1 0 0 1 0
Fiat X1-9 0 0 0 0 0 0 0
Porsche 914-2 0 0 0 0 0 0 0
Lotus Europa 0 0 0 0 0 0 0
Ford Pantera L 0 0 1 1 0 0 0
Ferrari Dino 0 0 0 0 0 0 0
Maserati Bora 0 0 0 1 0 0 0
Volvo 142E 0 0 0 0 0 0 0