从Pandas Groupby Dataframe创建等高线图

问题描述

我有以下熊猫数据框：

  p> 
 
 
  hdf = aggdf.groupby（['a'，'b']）。size（）
 hdf 
  
给我 
 
 
  ab 
 1 -2.0 1 
 -1.9 1 
 -1.8 1 
 -1.7 2 
 -1.6 5 
 -1.5 10 
 -1.4 9 
 -1.3 21 
 -1.2 34 
 -1.1 67 
 -1.0 65 
 -0.9 94 
 -0.8 180 
  - 0.7 242 
 -0.6 239 
 ... 
 187 0.4 22 
 0.5 10 
 188 -0.6 2 
 -0.5 2 
 -0.4 1 
 -0.3 2 
 -0.2 5 
 -0.1 10 
 -0.0 18 
 0.1 19 
 0.2 20 
 0.3 13 
 0.4 7 
 0.5 5 
 0.6 1 
长度：8844，dtype：int64 
  
 ，和你的帮助CT朱，然后我可以做
  hdfreset = hdf.reset_index（）
 hdfreset.columns = ['a'，'b'，'occurrence'] 
 hdfpivot = hdfreset.pivot（'a'，'b'）
  
，这最终给了我正确的值 
 
 
  X = hdfpivot.columns.levels [1] .values 
 Y = hdfpivot.index.values 
 Z = hdfpivot.values 
 Xi，Yi = np.meshgrid（X，Y）
 plt.contourf（Yi ，Xi，Z，alpha = 0.7，cmap = plt.cm.jet）; 
  
这导致了这个美丽的轮廓：
 
 
  
I have following Pandas Dataframe:
In [66]: hdf.size()
Out[66]:
a           b
0           0.0          21004
            0.1         119903
            0.2         186579
            0.3         417349
            0.4         202723
            0.5         100906
            0.6          56386
            0.7           6080
            0.8           3596
            0.9           2391
            1.0           1963
            1.1           1730
            1.2           1663
            1.3           1614
            1.4           1309
...
186         0.2         15
            0.3          9
            0.4         21
            0.5          4
187         0.2          3
            0.3         10
            0.4         22
            0.5         10
188         0.0         11
            0.1         19
            0.2         20
            0.3         13
            0.4          7
            0.5          5
            0.6          1
Length: 4572, dtype: int64
You see, a from 0...188 and b in every group from some value to some value. And as the designated Z-value, the count of the occurence of the pair a/b.
How to get a countour or heatmap plot out of the grouped dataframe?
I have this (asking for the ?):
numcols, numrows = 30, 30
xi = np.linspace(0, 200, numcols)
yi = np.linspace(0, 6, numrows)
xi, yi = np.meshgrid(xi, yi)
zi = griddata(?, ?, hdf.size().values, xi, yi)
How to get the x and y values out of the Groupby object and plot a contour?
 解决方案 
Thanks a lot! My fault was, that I did not realize, that I have to apply some function to the groupby dataframe, like .size(), to work with it...
hdf = aggdf.groupby(['a','b']).size()
hdf
gives me
a           b
1           -2.0          1
            -1.9          1
            -1.8          1
            -1.7          2
            -1.6          5
            -1.5         10
            -1.4          9
            -1.3         21
            -1.2         34
            -1.1         67
            -1.0         65
            -0.9         94
            -0.8        180
            -0.7        242
            -0.6        239
...
187          0.4        22
             0.5        10
188         -0.6         2
            -0.5         2
            -0.4         1
            -0.3         2
            -0.2         5
            -0.1        10
            -0.0        18
             0.1        19
             0.2        20
             0.3        13
             0.4         7
             0.5         5
             0.6         1
Length: 8844, dtype: int64
With that, and your help CT Zhu, I could then do
hdfreset = hdf.reset_index()
hdfreset.columns = ['a', 'b', 'occurrence']
hdfpivot=hdfreset.pivot('a', 'b')
and this finally gave me the correct values to
X=hdfpivot.columns.levels[1].values
Y=hdfpivot.index.values
Z=hdfpivot.values
Xi,Yi = np.meshgrid(X, Y)
plt.contourf(Yi, Xi, Z, alpha=0.7, cmap=plt.cm.jet);
which leads to this beautiful contourf:
                        
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