Add Line plot conditional line_color functionality

It would be very handy to be able to have conditional line colouring for a line plot in Bokeh.

It is supported for circle plots and other similar plots for the fill and line colour options.

Please see this issue on GitHub for further details.

Hi,

It's not clear what you are asking for. Line and circle are topologically very different. If you have a ColumnDataSource with columns of length 10, and you use it with Circle, then you get 10 circles drawn, and if you use a color mapper with that, then it color maps each value from some column and applies 10 different colors, one to each of the circles. But Line is not like that, The columns have 10 values in then, but only one line gets drawn. What is the actual goal in that case?

* Do you want to use the multiple values in the column to make a single "rainbow" line? i.e.that starts green at one end and orange at the other? If so, that is not supported by the underlying browser HTML canvas, so it's not supported by Bokeh either. It's possible you could write a custom extension to draw something like that.

* Otherwise, what does it mean to take a column of 10 values and use all 10 to color one line? There's not a generally meaningful interpretation of that. Maybe you have some specific use case where it makes sense to take a whole array of numbers and turn it in to one color or one like but that is something too specialized for a general library.

Alternatively, are you trying to draw multiple lines at once? Then you can use multi_line instead of line:

  https://bokeh.pydata.org/en/latest/docs/user_guide/plotting.html#multiple-lines

In that case it does make sense to apply a color mapper, because the mapper can generate 10 colors (just like with Circle, etc) and us one color for each of the multiple lines.

Thanks,

Bryan

···

On Jun 15, 2018, at 07:28, [email protected] wrote:

It would be very handy to be able to have conditional line colouring for a line plot in Bokeh.

It is supported for circle plots and other similar plots for the fill and line colour options.

Please see this issue on GitHub for further details.

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I’ve had a question related to applying a color map to a set of lines which has been answered here:

https://stackoverflow.com/questions/50192139/bokeh-apply-color-map-to-set-of-lines

···

On Friday, 15 June 2018 20:38:36 UTC+5:30, Bryan Van de ven wrote:

Hi,

It’s not clear what you are asking for. Line and circle are topologically very different. If you have a ColumnDataSource with columns of length 10, and you use it with Circle, then you get 10 circles drawn, and if you use a color mapper with that, then it color maps each value from some column and applies 10 different colors, one to each of the circles. But Line is not like that, The columns have 10 values in then, but only one line gets drawn. What is the actual goal in that case?

  • Do you want to use the multiple values in the column to make a single “rainbow” line? i.e.that starts green at one end and orange at the other? If so, that is not supported by the underlying browser HTML canvas, so it’s not supported by Bokeh either. It’s possible you could write a custom extension to draw something like that.

  • Otherwise, what does it mean to take a column of 10 values and use all 10 to color one line? There’s not a generally meaningful interpretation of that. Maybe you have some specific use case where it makes sense to take a whole array of numbers and turn it in to one color or one like but that is something too specialized for a general library.

Alternatively, are you trying to draw multiple lines at once? Then you can use multi_line instead of line:

    [https://bokeh.pydata.org/en/latest/docs/user_guide/plotting.html#multiple-lines](https://bokeh.pydata.org/en/latest/docs/user_guide/plotting.html#multiple-lines)

In that case it does make sense to apply a color mapper, because the mapper can generate 10 colors (just like with Circle, etc) and us one color for each of the multiple lines.

Thanks,

Bryan

On Jun 15, 2018, at 07:28, [email protected] wrote:

It would be very handy to be able to have conditional line colouring for a line plot in Bokeh.

It is supported for circle plots and other similar plots for the fill and line colour options.

Please see this issue on GitHub for further details.


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