matplotlib：不等间距刻度/特定颜色的零

Question

我一直在尝试解决一个问题，但无论是 stackoverflow 还是其他网站都无法帮助我。

我正在尝试使用具有 52 个离散步长的颜色条 gist_rainbow_r 绘制范围从 -40 到 36 的字段（轮廓）。如您所见，这些级别不是等距分布的。我想要的是一个带有等距刻度（所有级别应该等距）的颜色条，具有离散化的 52 gist_rainbow_r 颜色的颜色。这是可能吗？下面是代码片段。

    levels = [-40,-30,-20,-15,-12,-10,-9,-8,-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36]
    # define the colormap
    cmap = cm.get_cmap('gist_rainbow_r',52)
    # define the bins and normalize
    norm = mpl.colors.BoundaryNorm(levels, cmap.N)
    contourplot = map.contourf(xpoints,ypoints,fieldtoplot,range(-40,36),cmap=cmap,norm=norm,spacing='regular')

    ax = plt.gca()  # Gets the current axes
    divider = make_axes_locatable(ax)  # Lets us move axes around
    cax = divider.append_axes("bottom", size="2%",pad=-0.02,axes_class=maxes.Axes)  #Adds an axis for the colorbar
    F.add_axes(cax)  # Adds the new axis to the figure as the current working axis
    bar = plt.colorbar(contourplot,cax=cax,orientation='horizontal',spacing='regular',extend='both',extendfrac='auto',extendrect='True',format='%1i',ticks=levels, boundaries=levels) # Plots colorbar in new axis 
    bar.update_ticks()

此致

马丁

Answer 1

其实，解决方法很简单，写在这里有点尴尬……抱歉打扰了社区！

我们开始 - 这解决了我的问题：

levels = [-40,-30,-20,-15,-12,-10,-9,-8,-7,-6,-5,-4,-3,-2,-1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36]
# define the colormap
cmap = cm.get_cmap('gist_rainbow_r',52)
# define the bins and normalize
norm = mpl.colors.BoundaryNorm(levels, cmap.N)
contourplot = map.contourf(xpoints,ypoints,fieldtoplot,range(-40,36),cmap=cmap,norm=norm,spacing='uniform', levels=levels)

ax = plt.gca()  # Gets the current axes
divider = make_axes_locatable(ax)  # Lets us move axes around
cax = divider.append_axes("bottom", size="2%",pad=-0.02,axes_class=maxes.Axes)  #Adds an axis for the colorbar
F.add_axes(cax)  # Adds the new axis to the figure as the current working axis
bar = plt.colorbar(contourplot,cax=cax,orientation='horizontal',spacing='uniform',extend='both',extendfrac='auto',extendrect='True',format='%1i',ticks=levels, boundaries=levels) # Plots colorbar in new axis 
bar.update_ticks()

所以，要清楚：将“间距”设置为“统一”（而不是相等 - 通过查看 colorbar.py 我注意到这个设置根本不存在）并将“级别”传递给轮廓函数。

在这一点上：感谢@Saullo Castro 部分回答了这个问题！

干杯

马丁