Axes array for subplots

The following line is part of a much larger python (3.6) with Matplotlib
(2.2.2) program in which the number of subplots is determined from input
data:

fig, axarr = plt.subplots(NSub, figsize=(width,height), sharex=True)

This works fine when the number of subplots (NSub) is greater than 1.
For example when NSub=3, axarr is an array of length 3 and contains:

array([<matplotlib.axes._subplots.AxesSubplot object at
0x0000025900E9DDD8>,
??? <matplotlib.axes._subplots.AxesSubplot object at
0x00000259011897F0>,
??? <matplotlib.axes._subplots.AxesSubplot object at
0x00000259011C7128>],
??? dtype=object)

However, when NSub=1, axarr contains:

<matplotlib.axes._subplots.AxesSubplot object at 0x00000161AB26AE80>

and of course, will give an error if axarr is an array; i.e.

builtins.TypeError: 'AxesSubplot' object does not support indexing

For my code this requires special handling because axarr is no longer an
array. Why not have axarr contain:

array([<matplotlib.axes._subplots.AxesSubplot object at
0x00000161AB26AE80>],dtype=object)

when NSub=1. IMHO this is consistent; i.e. it is an array with a length
that is equal to the number of subplots.
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By default, `squeeze` is called on the array prior to returning it. This
way, users don't need to deal with 2D arrays when most of the time, they
are dealing with 1D setups. You can specify squeeze=False to subplots to
turn this behavior off and always have a 2D array.

I hope that helps!
Ben Root

···

On Tue, Apr 17, 2018 at 10:12 AM, Virgil Stokes <vs at it.uu.se> wrote:

The following line is part of a much larger python (3.6) with Matplotlib
(2.2.2) program in which the number of subplots is determined from input
data:

  fig, axarr = plt.subplots(NSub, figsize=(width,height), sharex=True)

This works fine when the number of subplots (NSub) is greater than 1. For
example when NSub=3, axarr is an array of length 3 and contains:

  array([<matplotlib.axes._subplots.AxesSubplot object at
0x0000025900E9DDD8>,
         <matplotlib.axes._subplots.AxesSubplot object at
0x00000259011897F0>,
         <matplotlib.axes._subplots.AxesSubplot object at
0x00000259011C7128>],
        dtype=object)

However, when NSub=1, axarr contains:

  <matplotlib.axes._subplots.AxesSubplot object at 0x00000161AB26AE80>

and of course, will give an error if axarr is an array; i.e.

  builtins.TypeError: 'AxesSubplot' object does not support indexing

For my code this requires special handling because axarr is no longer an
array. Why not have axarr contain:

  array([<matplotlib.axes._subplots.AxesSubplot object at
0x00000161AB26AE80>],dtype=object)

when NSub=1. IMHO this is consistent; i.e. it is an array with a length
that is equal to the number of subplots.

_______________________________________________
Matplotlib-users mailing list
Matplotlib-users at python.org
https://mail.python.org/mailman/listinfo/matplotlib-users

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Ok Ben,

I tried the following per your suggestion:

fig, axarr = plt.subplots(NSub, figsize=(width,height), squeeze=False,
sharex=True)

but when the following is executed:

? ax.grid(True)

I get the following error message:
? builtins.AttributeError: 'numpy.ndarray' object has no attribute 'grid'

But, thanks for your help :-).

···

On 2018-04-17 16:30, Benjamin Root wrote:

By default, `squeeze` is called on the array prior to returning it.
This way, users don't need to deal with 2D arrays when most of the
time, they are dealing with 1D setups. You can specify squeeze=False
to subplots to turn this behavior off and always have a 2D array.

I hope that helps!
Ben Root

On Tue, Apr 17, 2018 at 10:12 AM, Virgil Stokes <vs at it.uu.se > <mailto:vs at it.uu.se>> wrote:

    The following line is part of a much larger python (3.6) with
    Matplotlib (2.2.2) program in which the number of subplots is
    determined from input data:

    fig, axarr = plt.subplots(NSub, figsize=(width,height), sharex=True)

    This works fine when the number of subplots (NSub) is greater than
    1. For example when NSub=3, axarr is an array of length 3 and
    contains:

    array([<matplotlib.axes._subplots.AxesSubplot object at
    0x0000025900E9DDD8>,
    ??? <matplotlib.axes._subplots.AxesSubplot object at
    0x00000259011897F0>,
    ??? <matplotlib.axes._subplots.AxesSubplot object at
    0x00000259011C7128>],
    ??? dtype=object)

    However, when NSub=1, axarr contains:

    <matplotlib.axes._subplots.AxesSubplot object at 0x00000161AB26AE80>

    and of course, will give an error if axarr is an array; i.e.

    builtins.TypeError: 'AxesSubplot' object does not support indexing

    For my code this requires special handling because axarr is no
    longer an array. Why not have axarr contain:

    array([<matplotlib.axes._subplots.AxesSubplot object at
    0x00000161AB26AE80>],dtype=object)

    when NSub=1. IMHO this is consistent; i.e. it is an array with a
    length that is equal to the number of subplots.

    _______________________________________________
    Matplotlib-users mailing list
    Matplotlib-users at python.org <mailto:Matplotlib-users at python.org>
    https://mail.python.org/mailman/listinfo/matplotlib-users
    <https://mail.python.org/mailman/listinfo/matplotlib-users>

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Virgil,

How did you get from `axarr` to `ax`? The error message suggests that you
haven't fully indexed the result. Remember, with squeeze=False, `axarr`
will be a 2-D array, requiring two indices.

Ben

···

On Tue, Apr 17, 2018 at 11:14 AM, Virgil Stokes <vs at it.uu.se> wrote:

Ok Ben,

I tried the following per your suggestion:

  fig, axarr = plt.subplots(NSub, figsize=(width,height), squeeze=False,
sharex=True)

but when the following is executed:

  ax.grid(True)

I get the following error message:
  builtins.AttributeError: 'numpy.ndarray' object has no attribute 'grid'

But, thanks for your help :-).

On 2018-04-17 16:30, Benjamin Root wrote:

By default, `squeeze` is called on the array prior to returning it. This
way, users don't need to deal with 2D arrays when most of the time, they
are dealing with 1D setups. You can specify squeeze=False to subplots to
turn this behavior off and always have a 2D array.

I hope that helps!
Ben Root

On Tue, Apr 17, 2018 at 10:12 AM, Virgil Stokes <vs at it.uu.se> wrote:

The following line is part of a much larger python (3.6) with Matplotlib
(2.2.2) program in which the number of subplots is determined from input
data:

  fig, axarr = plt.subplots(NSub, figsize=(width,height), sharex=True)

This works fine when the number of subplots (NSub) is greater than 1. For
example when NSub=3, axarr is an array of length 3 and contains:

  array([<matplotlib.axes._subplots.AxesSubplot object at
0x0000025900E9DDD8>,
         <matplotlib.axes._subplots.AxesSubplot object at
0x00000259011897F0>,
         <matplotlib.axes._subplots.AxesSubplot object at
0x00000259011C7128>],
        dtype=object)

However, when NSub=1, axarr contains:

  <matplotlib.axes._subplots.AxesSubplot object at 0x00000161AB26AE80>

and of course, will give an error if axarr is an array; i.e.

  builtins.TypeError: 'AxesSubplot' object does not support indexing

For my code this requires special handling because axarr is no longer an
array. Why not have axarr contain:

  array([<matplotlib.axes._subplots.AxesSubplot object at
0x00000161AB26AE80>],dtype=object)

when NSub=1. IMHO this is consistent; i.e. it is an array with a length
that is equal to the number of subplots.

_______________________________________________
Matplotlib-users mailing list
Matplotlib-users at python.org
https://mail.python.org/mailman/listinfo/matplotlib-users

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ax is used in a function that references axarr. My problem is not about
2D arrays.

--V

···

On 2018-04-17 17:22, Benjamin Root wrote:

Virgil,

How did you get from `axarr` to `ax`? The error message suggests that
you haven't fully indexed the result. Remember, with squeeze=False,
`axarr` will be a 2-D array, requiring two indices.

Ben

On Tue, Apr 17, 2018 at 11:14 AM, Virgil Stokes <vs at it.uu.se > <mailto:vs at it.uu.se>> wrote:

    Ok Ben,

    I tried the following per your suggestion:

    fig, axarr = plt.subplots(NSub, figsize=(width,height),
    squeeze=False, sharex=True)

    but when the following is executed:

    ? ax.grid(True)

    I get the following error message:
    builtins.AttributeError: 'numpy.ndarray' object has no attribute
    'grid'

    But, thanks for your help :-).

    On 2018-04-17 16:30, Benjamin Root wrote:

    By default, `squeeze` is called on the array prior to returning
    it. This way, users don't need to deal with 2D arrays when most
    of the time, they are dealing with 1D setups. You can specify
    squeeze=False to subplots to turn this behavior off and always
    have a 2D array.

    I hope that helps!
    Ben Root

    On Tue, Apr 17, 2018 at 10:12 AM, Virgil Stokes <vs at it.uu.se >> <mailto:vs at it.uu.se>> wrote:

        The following line is part of a much larger python (3.6) with
        Matplotlib (2.2.2) program in which the number of subplots is
        determined from input data:

        fig, axarr = plt.subplots(NSub, figsize=(width,height),
        sharex=True)

        This works fine when the number of subplots (NSub) is greater
        than 1. For example when NSub=3, axarr is an array of length
        3 and contains:

        array([<matplotlib.axes._subplots.AxesSubplot object at
        0x0000025900E9DDD8>,
        <matplotlib.axes._subplots.AxesSubplot object at
        0x00000259011897F0>,
        <matplotlib.axes._subplots.AxesSubplot object at
        0x00000259011C7128>],
        ??? dtype=object)

        However, when NSub=1, axarr contains:

        <matplotlib.axes._subplots.AxesSubplot object at
        0x00000161AB26AE80>

        and of course, will give an error if axarr is an array; i.e.

        builtins.TypeError: 'AxesSubplot' object does not support
        indexing

        For my code this requires special handling because axarr is
        no longer an array. Why not have axarr contain:

        array([<matplotlib.axes._subplots.AxesSubplot object at
        0x00000161AB26AE80>],dtype=object)

        when NSub=1. IMHO this is consistent; i.e. it is an array
        with a length that is equal to the number of subplots.

        _______________________________________________
        Matplotlib-users mailing list
        Matplotlib-users at python.org <mailto:Matplotlib-users at python.org>
        https://mail.python.org/mailman/listinfo/matplotlib-users
        <https://mail.python.org/mailman/listinfo/matplotlib-users>

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Virgil, I will be very specific: The following all references the copy of
Plotting_Test03.py you sent me.

At line 263, you have a comment: "# The Axes array (axarr) will be a list
of NSub objects (an axis for each subplot)". This is incorrect. `axarr` is
not a list, but a numpy array *or scalar*. When plt.subplots(1) is called,
you get a numpy scalar, which is the problem that you originally approached
us about. When plt.subplots(2) is called, you get a 1D numpy array, which
looks a lot like a list.

However, if plt.subplots(2, squeeze=False) is called, then you get a *2D*
numpy array of axes, of shape (2, 1). That is because plt.subplots(), in
the general case, is used for specifying the number of rows and columns of
subplots, so without squeezing, the axes array is 2D.

Therefore, if you have squeeze=False turned on in plt.subplots(), then line
306 needs to change to `ax = axarr[j, 0]`. Similar to line 318, and the
area around line 331.

Ben Root

···

On Tue, Apr 17, 2018 at 2:26 PM, Virgil Stokes <vs at it.uu.se> wrote:

ax is used in a function that references axarr. My problem is not about 2D
arrays.

--V

On 2018-04-17 17:22, Benjamin Root wrote:

Virgil,

How did you get from `axarr` to `ax`? The error message suggests that you
haven't fully indexed the result. Remember, with squeeze=False, `axarr`
will be a 2-D array, requiring two indices.

Ben

On Tue, Apr 17, 2018 at 11:14 AM, Virgil Stokes <vs at it.uu.se> wrote:

Ok Ben,

I tried the following per your suggestion:

  fig, axarr = plt.subplots(NSub, figsize=(width,height), squeeze=False,
sharex=True)

but when the following is executed:

  ax.grid(True)

I get the following error message:
  builtins.AttributeError: 'numpy.ndarray' object has no attribute 'grid'

But, thanks for your help :-).

On 2018-04-17 16:30, Benjamin Root wrote:

By default, `squeeze` is called on the array prior to returning it. This
way, users don't need to deal with 2D arrays when most of the time, they
are dealing with 1D setups. You can specify squeeze=False to subplots to
turn this behavior off and always have a 2D array.

I hope that helps!
Ben Root

On Tue, Apr 17, 2018 at 10:12 AM, Virgil Stokes <vs at it.uu.se> wrote:

The following line is part of a much larger python (3.6) with Matplotlib
(2.2.2) program in which the number of subplots is determined from input
data:

  fig, axarr = plt.subplots(NSub, figsize=(width,height), sharex=True)

This works fine when the number of subplots (NSub) is greater than 1.
For example when NSub=3, axarr is an array of length 3 and contains:

  array([<matplotlib.axes._subplots.AxesSubplot object at
0x0000025900E9DDD8>,
         <matplotlib.axes._subplots.AxesSubplot object at
0x00000259011897F0>,
         <matplotlib.axes._subplots.AxesSubplot object at
0x00000259011C7128>],
        dtype=object)

However, when NSub=1, axarr contains:

  <matplotlib.axes._subplots.AxesSubplot object at 0x00000161AB26AE80>

and of course, will give an error if axarr is an array; i.e.

  builtins.TypeError: 'AxesSubplot' object does not support indexing

For my code this requires special handling because axarr is no longer an
array. Why not have axarr contain:

  array([<matplotlib.axes._subplots.AxesSubplot object at
0x00000161AB26AE80>],dtype=object)

when NSub=1. IMHO this is consistent; i.e. it is an array with a length
that is equal to the number of subplots.

_______________________________________________
Matplotlib-users mailing list
Matplotlib-users at python.org
https://mail.python.org/mailman/listinfo/matplotlib-users

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Hi Virgil,

I suspect that should you are using something like

ax = axarr[i]

while `squeeze=False` will require that you use

ax = axarr[i, 0]

(from what I understood from you example).

Please find attached a code snippet that should hopefully better
demonstrate this.

Best regards,
Adrien

ax is used in a function that references axarr. My problem is not about
2D arrays.

--V

Virgil,

How did you get from `axarr` to `ax`? The error message suggests that
you haven't fully indexed the result. Remember, with squeeze=False,
`axarr` will be a 2-D array, requiring two indices.

Ben

    Ok Ben,

    I tried the following per your suggestion:

    fig, axarr = plt.subplots(NSub, figsize=(width,height),
    squeeze=False, sharex=True)

    but when the following is executed:

    ? ax.grid(True)

    I get the following error message:
    builtins.AttributeError: 'numpy.ndarray' object has no attribute
    'grid'

    But, thanks for your help :-).

    By default, `squeeze` is called on the array prior to returning
    it. This way, users don't need to deal with 2D arrays when most
    of the time, they are dealing with 1D setups. You can specify
    squeeze=False to subplots to turn this behavior off and always
    have a 2D array.

    I hope that helps!
    Ben Root

        The following line is part of a much larger python (3.6) with
        Matplotlib (2.2.2) program in which the number of subplots is
        determined from input data:

        fig, axarr = plt.subplots(NSub, figsize=(width,height),
        sharex=True)

        This works fine when the number of subplots (NSub) is greater
        than 1. For example when NSub=3, axarr is an array of length
        3 and contains:

        array([<matplotlib.axes._subplots.AxesSubplot object at
        0x0000025900E9DDD8>,
        <matplotlib.axes._subplots.AxesSubplot object at
        0x00000259011897F0>,
        <matplotlib.axes._subplots.AxesSubplot object at
        0x00000259011C7128>],
        ??? dtype=object)

        However, when NSub=1, axarr contains:

        <matplotlib.axes._subplots.AxesSubplot object at
        0x00000161AB26AE80>

        and of course, will give an error if axarr is an array; i.e.

        builtins.TypeError: 'AxesSubplot' object does not support
        indexing

        For my code this requires special handling because axarr is
        no longer an array. Why not have axarr contain:

        array([<matplotlib.axes._subplots.AxesSubplot object at
        0x00000161AB26AE80>],dtype=object)

        when NSub=1. IMHO this is consistent; i.e. it is an array
        with a length that is equal to the number of subplots.

        _______________________________________________
        Matplotlib-users mailing list
        Matplotlib-users at python.org <mailto:Matplotlib-users at python.org>
        https://mail.python.org/mailman/listinfo/matplotlib-users
        <https://mail.python.org/mailman/listinfo/matplotlib-users>

_______________________________________________
Matplotlib-users mailing list
Matplotlib-users at python.org
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···

On 04/17/2018 11:26 AM, Virgil Stokes wrote:

On 2018-04-17 17:22, Benjamin Root wrote:

On Tue, Apr 17, 2018 at 11:14 AM, Virgil Stokes <vs at it.uu.se >> <mailto:vs at it.uu.se>> wrote:
    On 2018-04-17 16:30, Benjamin Root wrote:

    On Tue, Apr 17, 2018 at 10:12 AM, Virgil Stokes <vs at it.uu.se >>> <mailto:vs at it.uu.se>> wrote: