I found some code to generate a set of small multiples and it is working perfectly.

fig, axes = plt.subplots(6,3, figsize=(21,21)) fig.subplots_adjust(hspace=.3, wspace=.175) for ax, data in zip(axes.ravel(), clean_sets): ax.plot(data.ETo, "o")

The line `for ax, data in zip(axes.ravel(), clean_sets):`

contians `.ravel()`

but I do not understand what this is actually doing or why it is necessary.

**If I take a look at the docs I find the following:**

Return a contiguous flattened array.

A 1-D array, containing the elements of the input, is returned. A copy is made only if needed.

I guess the return that corresponds to axes from `plt.subplot()`

is a multidimensional array that can’t be iterated over, but really I’m not sure. A simple explanation would be greatly appreciated.

**What is the purpose of using .ravel() in this case?**

## Advertisement

## Answer

Your guess is correct. `plt.subplots()`

returns either an `Axes`

or a `numpy`

array of several axes, depending on the input. In case a 2D grid is defined by the arguments `nrows`

and `ncols`

, the returned `numpy`

array will be a 2D array as well.

This behaviour is explained in the `pyplot.subplots`

documentation inside the `squeeze`

argument,

`squeeze`

: bool, optional, default: True

If True, extra dimensions are squeezed out from the returned Axes object:

- if only one subplot is constructed (nrows=ncols=1), the resulting single Axes object is returned as a scalar.

- for Nx1 or 1xN subplots, the returned object is a 1D numpy object array of Axes objects are returned as numpy 1D arrays.
- for NxM, subplots with N>1 and M>1 are returned as a 2D arrays.

If False, no squeezing at all is done: the returned Axes object is always a 2D array containing Axes instances, even if it ends up being 1×1.

Since here you have `plt.subplots(6,3)`

and hence `N>1, M>1`

, the resulting object is necessarily a 2D array, independent of what `squeeze`

is set to.

This makes it necessary to flatten this array in order to be able to `zip`

it. Options are

`zip(axes.ravel())`

`zip(axes.flatten())`

`zip(axes.flat)`

**1**People found this is helpful