Axes from plt.subplots() is a “numpy.ndarray” object and has no attribute “plot”

问题:

The information below may be superfluous if you are trying to understand the error message. Please start off by reading the answer by @user707650

Using MatPlotLib, I wanted a generalizable script that creates the following from my data.

A window containing a subplots arranged so that there are b subplots per column. I want to be able to change the values of a and b.

If I have data for 2a subplots, I want 2 windows, each with the previously described "a subplots arranged according to b subplots per column".

The x and y data I am plotting are floats stored in np.arrays and are structured as follows:

• The x data is always the same for all plots and is of length 5.

   'x_vector': [0.000, 0.005, 0.010, 0.020, 0.030, 0.040] 

• The y data of all plots are stored in y_vector where the data for the first plot is stored at indexes 0 through 5. The data for the second plot is stored at indexes 6 through 11. The third plot gets 12-18, the fourth 19-24, and so on.

In total, for this dataset, I have 91 plots (i.e. 91*6 = 546 values stored in y_vector).

Attempt:

import matplotlib.pyplot as plt  # Options: plots_tot = 14 # Total number of plots. In reality there is going to be 7*13 = 91 plots. location_of_ydata = 6 # The values for the n:th plot can be found in the y_vector at index 'n*6' through 'n*6 + 6'. plots_window = 7 # Total number of plots per window. rows = 2 # Number of rows, i.e. number of subplots per column.  # Calculating number of columns: prim_cols = plots_window / rows extra_cols = 0 if plots_window % rows > 0:     extra_cols = 1 cols = prim_cols + extra_cols  print 'cols:', cols print 'rows:', rows  # Plotting: n=0 x=0 fig, ax = plt.subplots(rows, cols) while x <= plots_tot:     ax[x].plot(x_vector, y_vector[n:(n+location_of_ydata)], 'ro')     if x % plots_window == plots_window - 1:         plt.show() # New window for every 7 plots.     n = n+location_of_ydata     x = x+1 

I get the following error:

cols: 4 rows: 2 Traceback (most recent call last):   File "Script.py", line 222, in <module>     ax[x].plot(x_vector, y_vector[n:(n+location_of_ydata)], 'ro') AttributeError: 'numpy.ndarray' object has no attribute 'plot' 

回答1:

If you debug your program by simply printing ax, you'll quickly find out that ax is a two-dimensional array: one dimension for the rows, one for the columns.

Thus, you need two indices to index ax to retrieve the actual AxesSubplot instance, like:

ax[1,1].plot(...) 

If you want to iterate through the subplots in the way you do it now, by flattening ax first:

ax = ax.flatten() 

and now ax is a one dimensional array. I don't know if rows or columns are stepped through first, but if it's the wrong around, use the transpose:

ax = ax.T.flatten() 

---

Of course, by now it makes more sense to simply create each subplot on the fly, because that already has an index, and the other two numbers are fixed:

for x < plots_tot:      ax = plt.subplot(nrows, ncols, x+1) 

Note: you have x <= plots_tot, but with x starting at 0, you'll get an IndexError next with your current code (after flattening your array). Matplotlib is (unfortunately) 1-indexed for subplots. I prefer using a 0-indexed variable (Python style), and just add +1 for the subplot index (like above).

文章来源: Axes from plt.subplots() is a “numpy.ndarray” object and has no attribute “plot”