Null output when printing heatmap.2 object in rmarkdown

Question

I'm using rmarkdown via R-Studio and want to plot a heatmap by the heatmap.2. When I change the angle of column labels via the strCol option I get a NULL message printed before the heatmap in the output PDF file.
Attached a minimal code reproduce the problem:

{r, message=FALSE,warning=FALSE, echo=FALSE}
require(gplots)
data(mtcars)
x  <- as.matrix(mtcars)
heatmap.2(x,srtCol=0)

The PDF look like

Is there any way to remove this NULL from the PDF output?

score 2 · Accepted Answer · edited May 23 '17 at 12:31

Try the following modification using capture.output. This did not print NULL for me.

```{r, message=FALSE,warning=FALSE, echo=FALSE}
require(gplots)
data(mtcars)
x  <- as.matrix(mtcars)
res <- capture.output(heatmap.2(x,srtCol=0))
```

There may be a better way with some option to heatmap.2 but I didn't see it in the documentation. This was based off of the following SO post Suppress one command's output in R.

Null output when printing heatmap.2 object in rmarkdown

1 Answers1