How to include a colorscale for color of line graphs

📊 Plotly Python
2

Hi msuths1,

Plotly does not provide the colorscale attribute for lines of a scatter trace, of mode='lines'.
Even heatmap, contour and surface don’t return the color code in a colorscale corresponding to a z-value.

For your vectors you can use a custom function that returns the color for each particular value in an interval.
To call such a function you have first to choose from plotly.colors https://github.com/plotly/plotly.py/tree/master/packages/python/plotly/_plotly_utils/colors
a list of colors, pl_colors, for a colorscale:

from plotly.colors import * 

pl_colors = cmocean.deep  # define the deep colorsale

The custom function:

from ast import literal_eval
import numpy as np
def get_color_for_val(val, vmin, vmax, pl_colors):
    
    if pl_colors[0][:3] != 'rgb':
        raise ValueError('This function works only with Plotly  rgb-colorscales')
    if vmin >= vmax:
        raise ValueError('vmin should be < vmax')
    
    scale = [k/(len(pl_colors)-1) for k in range(len(pl_colors))] 
   
   
    colors_01 = np.array([literal_eval(color[3:]) for color in pl_colors])/255.  #color codes in [0,1]
   
    v= (val - vmin) / (vmax - vmin) # val is mapped to v in [0,1]
    #find two consecutive values in plotly_scale such that   v is in  the corresponding interval
    idx = 1
   
    while(v > scale[idx]): 
        idx += 1
    vv = (v - scale[idx-1]) / (scale[idx] -scale[idx-1] )
    
    #get   [0,1]-valued color code representing the rgb color corresponding to val
    val_color01 = colors_01[idx-1] + vv * (colors_01[idx ] - colors_01[idx-1])
    val_color_0255 = (255*val_color01+0.5).astype(int)
    return f'rgb{str(tuple(val_color_0255))}'

Example:

get_color_for_val(2.3, 1, 5, pl_colors)

returns 'rgb(62, 81, 157)'

In your case vmin, vmax are the min, respectively the max value in the column cos2.

Unfortunately you cannot plot a naturally associated colorbar. To get it displayed you should define a dummy Scatter trace, mode='markers', with two markers, of size= 0, and marker['color']=[vmin, vmax].