apply ecdf function to each column in dataframe and plot

Question

I want to apply my custom ecdf function on each column in a dataframe, then plot the ecdf based on the returned x,y values

the custom function:

def ecdf(df):
    n = len(df)
    x = np.sort(df)
    y = np.arange(1, n+1)/n
    return x, y

my attempt at a for loop:

for col in sj_interpol_data.columns:
   x_col, y_col = ecdf(col)
   ax = plt.figure()
   ax = plt.plot(x_col, y_col, marker='.', linestyle='none')
   ax = plt.margins=(0.02)
   plt.show()

Edited to include error:

AxisError                                 Traceback (most recent call last)
<ipython-input-75-d03c4fa0a973> in <module>()
      2 #design a for-loop which applies ecdf() on each column in df and plots them separately
      3 for col in sj_interpol_data.columns:
----> 4     x_col, y_col = ecdf(col)
      5     ax = plt.figure()
      6     ax = plt.plot(x_col, y_col, marker='.', linestyle='none')

<ipython-input-32-353fb281e367> in ecdf(df)
      4     n = len(df)
      5     #define x values - sorted values in array
----> 6     x = np.sort(df)
      7     #define y values - maps location of each datapoint WR to their percentiles
      8     y = np.arange(1, n+1)/n

C:\Anaconda3\lib\site-packages\numpy\core\fromnumeric.py in sort(a, axis, kind, order)
    845     else:
    846         a = asanyarray(a).copy(order="K")
--> 847     a.sort(axis=axis, kind=kind, order=order)
    848     return a
    849 

AxisError: axis -1 is out of bounds for array of dimension 0

Any advice on how to write this function so it can be applied to all columns in a dataframe and automatically plot in a for loop?

Answer 1

您将列名传递给ecdf函数，但您想将数据帧传递给它，至少这是函数定义所指示的。

Answer 2

I figured out the answer. I use df.sort_values() in the ecdf function, which uses pandas to sort values instead of numpy

so the modified function is:

def ecdf(df):
    n = len(df)
    x = df.sort_values()
    y = np.arange(1, n+1)/n
    return x, y

after applyting the for loop (shown above), the output resulted in separate ecdf plots for each column in the dataframe