colormap_milagro¶

gammapy.visualization.colormap_milagro(transition=0.5, width=0.0001, huestart=0.6)[source]¶

Colormap often used in Milagro collaboration publications.

This colormap is gray below transition and similar to the jet colormap above.

A sharp gray -> color transition is often used for significance images with a transition value of transition ~ 5 or transition ~ 7, so that the following effect is achieved:

gray: non-significant features are not well visible
color: significant features at the detection threshold transition

Note that this colormap is often criticised for over-exaggerating small differences in significance below and above the gray - color transition threshold.

The transition parameter is defined between 0 and 1. To calculate the value from data units an ImageNormalize instance should be used (see example below).

Parameters

transitionfloat (default = 0.5): Transition value (below: gray, above: color).
widthfloat (default = 0.0001): Width of the transition
huestartfloat (default = 0.6): Hue of the color at transition

Returns

colormapLinearSegmentedColormap: Colormap

Examples

>>> from gammapy.visualization import colormap_milagro
>>> from astropy.visualization.mpl_normalize import ImageNormalize
>>> from astropy.visualization import LinearStretch
>>> normalize = ImageNormalize(vmin=-5, vmax=15, stretch=LinearStretch())
>>> transition = normalize(5)
>>> cmap = colormap_milagro(transition=transition)