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rheatmapr-markdowngplots

Null output when printing heatmap.2 object in rmarkdown

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

enter image description here

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

Solution

  • 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.