Set Size of Plot in IHaskell (Jupyter) with Chart Package

I am able to do a simple 2D plot inside a Jupyter Notebook (with IHaskell) using the Haskell Chart Package. The code is here,

import Graphics.Rendering.Chart.Easy
cData = [1,2,3,4,3,2,1]
toRenderable  $ do
    layout_title .= "Recovered Signal"
    layout_x_axis . laxis_title .= "Time (msecs)"
    layout_y_axis . laxis_title .= "Original Input Level"
    plot (line "Amplitude" [zip [0,1..] cData])

The plot is automatically displayed in a Jupyter cell when the code cell returns a 'Renderable'

I would like to make the plot smaller.

I've tried,

• Looking through all the examples on the Wiki but the only size option I saw was with file output.
• I went through the Chart function index looking for 'size', 'width' and found nothing relevant
• I even asked ChatGPT (sorry if that's a bad word) and it failed.
• Google was no help. You can change font size but not the plot size.
• I did find 'plotsToRenderable' which mentions a 'minsize' but it didn't make sense to me.

I'm a mid-level Haskeller but never learned lenses which may be part of my problem. Maybe it's time to learn ..

Any help appreciated!

Tom

Lenses won't help you much... the problem is that IHaskell.Display.Charts hard-codes width and height. It's a bit silly...

What you could do is write your own wrapper type for custom-sized charts, and copy the instances with the specified sizes.

import           System.Directory
import           Data.Default.Class
import           Graphics.Rendering.Chart.Renderable
import           Graphics.Rendering.Chart.Backend.Cairo
import qualified Data.ByteString.Char8 as Char
import           System.IO.Unsafe

import           IHaskell.Display

data SizedRenderable a = Sized
  { size :: (Width, Height)
  , theChart :: Renderable a
  }

instance IHaskellDisplay (SizedRenderable a) where
  display renderable = do
    pngDisp <- chartData renderable PNG

    -- We can add `svg svgDisplay` to the output of `display`, but SVGs are not resizable in the IPython
    -- notebook.
    svgDisp <- chartData renderable SVG

    return $ Display [pngDisp, svgDisp]

chartData :: Renderable a -> FileFormat -> IO DisplayData
chartData (Sized size@(w,h) renderable) format = do
  switchToTmpDir

  -- Write the PNG image.
  let filename = ".ihaskell-chart.png"
      opts = def { _fo_format = format, _fo_size = size }
  mkFile opts filename renderable

  -- Convert to base64.
  imgData <- Char.readFile filename
  return $
    case format of
      PNG -> png w h $ base64 imgData
      SVG -> svg $ Char.unpack imgData


-- TODO add signature, I can't be bothered to look it up
mkFile opts filename renderable = renderableToFile opts filename renderable