# make_mapping_array¶

make_mapping_array(N, data, gamma=1.0, inverse=False)[source]

Similar to makeMappingArray but permits circular hue gradations along 0-360, disables clipping of out-of-bounds channel values, and uses fancier “gamma” scaling.

Parameters
• N (int) – Number of points in the colormap lookup table.

• data (2D array-like) – List of $$(x, y_0, y_1)$$ tuples specifying the channel jump (from $$y_0$$ to $$y_1$$) and the $$x$$ coordinate of that transition (ranges between 0 and 1). See LinearSegmentedColormap for details.

• gamma (float or list of float, optional) – To obtain channel values between coordinates $$x_i$$ and $$x_{i+1}$$ in rows $$i$$ and $$i+1$$ of data, we use the formula:

$y = y_{1,i} + w_i^{\gamma_i}*(y_{0,i+1} - y_{1,i})$

where $$\gamma_i$$ corresponds to gamma and the weight $$w_i$$ ranges from 0 to 1 between rows i and i+1. If gamma is float, it applies to every transition. Otherwise, its length must equal data.shape-1.

This is like the gamma used with matplotlib’s makeMappingArray, except it controls the weighting for transitions between each segment data coordinate rather than the coordinates themselves. This makes more sense for PerceptuallyUniformColormap\ s because they usually consist of just one linear transition for sequential colormaps and two linear transitions for diverging colormaps – and in the latter case, it is often desirable to modify both “halves” of the colormap in the same way.

• inverse (bool, optional) – If True, $$w_i^{\gamma_i}$$ is replaced with $$1 - (1 - w_i)^{\gamma_i}$$ – that is, when gamma is greater than 1, this weights colors toward higher channel values instead of lower channel values.

This is implemented in case we want to apply equal “gamma scaling” to different HSL channels in different directions. Usually, this is done to weight low data values with higher luminance and lower saturation, thereby emphasizing “extreme” data values with stronger colors.