Why is the histogram object printed when the histogram is called in j?

Question

set.seed(120834)
DT <- data.table(var = rnorm(100))

For comparison:

> hist(DT[ , var]) #of course plot is drawn

FROM

> DT[ , hist(var)]
$breaks
 [1] -3.0 -2.5 -2.0 -1.5 -1.0 -0.5  0.0  0.5  1.0  1.5  2.0  2.5

$counts
 [1]  1  1  6  7 16 20 20 12 12  3  2

$density
 [1] 0.02 0.02 0.12 0.14 0.32 0.40 0.40 0.24 0.24 0.06 0.04

$mids
 [1] -2.75 -2.25 -1.75 -1.25 -0.75 -0.25  0.25  0.75  1.25  1.75  2.25

$xname
[1] "var"

$equidist
[1] TRUE

attr(,"class")
[1] "histogram"

Why histdoes the latter print the object returned but not the first? Is there any way to suppress this?

I see in the code for hist.defaultthat the object is returned invisibly:

if (plot) {
        plot(r, freq = freq1, col = col, border = border, angle = angle, 
            density = density, main = main, xlim = xlim, ylim = ylim, 
            xlab = xlab, ylab = ylab, axes = axes, labels = labels, 
            ...)
        invisible(r)
    }

(And looking at the error from DT[ , hist(var, NA)]confirms [.data.table, really causes hist.default)

So how [.data.tabledid you manage to execute this invisible callback? Is it possible that an invisible object invisibly returns to a hidden environment, but an object from this environment is then explicitly displayed?

Answer 1

This is a known mistake, and at the moment there is no known solution or does not plan to fix it.

. GH Issue # 482 .

---

Matt -

:

DT[ , {hist(var);NULL}]

invisible(DT[,hist(var)])

, , 2.18 : "2.18 Im j , Im - . ?" , -. - R ( FAQ 2.22)