Add arrows at the end of x and y axis

[adamkk]

Hi,

After long time searching this issue, I need to ask this request. In my academic work, each chart needs to have x and y axis ending in arrows. Example: http://www.policonomics.com/supply-and-demand/

How can I add this to my ggplot2 charts?

Best,

[thomasp85]

@hadley what do you think of this? It's rather straightforward to add an arrow argument to element_line() which would make this possible... The grob placements will not be affected by the added width/height from the arrows so it should be a safe change...

[adamkk]

Dear @hadley,

perhaps line_type in element_line() could be changed from: "An integer or name: 0 = blank, 1 = solid, 2 = dashed, 3 = dotted, 4 = dotdash, 5 = longdash, 6 = two dash", to 1.... through 7= solidarrow ?

[thomasp85]

That would be the wrong approach - the arguments should map directly to polylineGrob so that element_line would gain an arrow argument that would get passed along in element_grob.element_line()

[hadley]

My only concern would be that there might be clipping issues — I can't remember where/when the axes are drawn. If that's not a problem, go ahead and add it.

[thomasp85]

My cursory investigation shows no clipping problems so I'll make a PR

[adamkk]

Thanks for the arrows. They look great !

Today, I have replicated the chart in RStudio with arrows using theme() and element_line(arrow=arrow()). Yet, while using theme_bw() it did not work. Is the element_line an attribute to one theme only, or all themes can make use of it?

Question: how I can get a clear background on the chart (without gray background and grid)?
See link: http://www.policonomics.com/supply-and-demand/

Best,
Adam

[hadley]

@adamkk a better place for questions of that nature is the ggplot2 mailing list