Add x,y kwargs for plot.line(). #1926

dcherian · 2018-02-20T06:04:35Z

Partially closes 1D line plot with data on the x axis #575
Tests added
Tests passed
Fully documented, including whats-new.rst for all changes and api.rst for new API

Description

plot.line now supports both 1D and 2D DataArrays as input. I've changed some variable names to make code clearer:

set xplt, yplt to be values that are passed to ax.plot()
xlabel, ylabel are axes labels
xdim, ydim are dimension names

Example

This code

da = xr.DataArray(np.cos(z), dims=['z'], coords=[z], name='f')

xy = [[None, None],
     [None, 'f'],
     [None, 'z'],
     ['f', None],
      ['z', None],
      ['z', 'f'],
      ['f', 'z']]

f, ax = plt.subplots(2,4)

for aa, (x,y) in enumerate(xy):
    da.plot(x=x, y=y, ax=ax.flat[aa])
    ax.flat[aa].set_title('x='+str(x)+ ' | '+'y='+str(y))

yields

Feedback requested

Should I refactor out the kwarg checking?

stickler-ci · 2018-02-20T06:04:55Z

xarray/plot/plot.py

-    _ensure_plottable(x)
+        else:
+            if x is not None and x is not darray.name:
+                raise ValueError('Cannot make a line plot with x=%r, y=%r and hue=%r'


E501 line too long (85 > 79 characters)

fmaussion

Thanks @dcherian ! I have a couple of comments and a general question: do we want to add the control via variable name? I think it makes things more confusing for little added value (names have no control on other plots such as 2D plots).

Otherwise this looks quite good!

fmaussion · 2018-02-20T21:00:13Z

doc/plotting.rst

@@ -197,6 +197,16 @@ It is required to explicitly specify either
 Thus, we could have made the previous plot by specifying ``hue='lat'`` instead of ``x='time'``.
 If required, the automatic legend can be turned off using ``add_legend=False``.

+Data along x-axis


"Rotated line plots" as title? Just a suggestion

Rotation makes me think of rotating the lines by an angle. How about "Coordinate along y-axis"?

fmaussion · 2018-02-20T21:00:48Z

doc/plotting.rst

+Data along x-axis
+~~~~~~~~~~~~~~~~~
+
+It is also possible to make line plots such that the data are on the x-axis and a co-ordinate is on the y-axis. This can be done by specifying the ``x`` and ``y`` keyword arguments.


"co-ordinate" -> coordinate

fmaussion · 2018-02-20T21:01:30Z

doc/whats-new.rst

@@ -97,6 +97,8 @@ Enhancements
  encoding/decoding of datetimes with non-standard calendars without the
  netCDF4 dependency (:issue:`1084`).
  By `Joe Hamman <https://github.com/jhamman>`_.
+- :py:func:`~plot.line()` learned to make plots with data on x-axis if so specified.


add (:issue:`575`)

fmaussion · 2018-02-20T21:03:06Z

xarray/plot/plot.py

+        1D and 2D DataArrays: Coordinate for x axis.
+    y : string, optional
+        1D DataArray: Can be coordinate name or DataArray.name
+        2D DataArray: Coordinate for y axis.


I'm not sure this is really helping. I'd prefer to stick to the simple Coordinate for x/y axis.

fmaussion · 2018-02-20T21:06:11Z

xarray/plot/plot.py

+        if x is not None and y is not None and x == y:
+            raise ValueError('Cannot make a plot with x=%r and y=%r' % (x, y))
+
+        if (x is None and y is None) or x == dim or y is darray.name:


y is darray.name -> y == darray.name

fmaussion · 2018-02-20T21:06:23Z

xarray/plot/plot.py

+            xlabel = dim
+            ylabel = darray.name
+
+        elif y == dim or x is darray.name:


dcherian · 2018-02-20T23:04:59Z

@fmaussion when I added the hue argument, @shoyer suggested that we have a "fully explicit way to make these plots".
In this case this would mean
da.plot(x='temp', y='time', hue='lat')
which seems a lot more readable than
da.plot(y='coordinate', hue='lat')

It would also mean that x,y are different from hue (for hue we do specify dimension name).

@shoyer Thoughts?

EDIT:

@fmaussion Do you mean da.plot(y='time', x=None, hue='lat')?

fmaussion · 2018-02-21T15:12:19Z

Do you mean da.plot(y='time', x=None, hue='lat')

Yes, I meant that there should be one and only way to specify which axis should do what: my understanding of your current implementation is that there are two ways to reach the same goal: either by (i) specifying the name of the variable to the axis you want to plot it onto, or (ii) by specifying the name of the coordinate you want to use for the axis. Since (ii) is the default and only option for 1D and 2D plots until now, I just wondered if (i) is very necessary. (or maybe I missed something)

shoyer · 2018-02-21T16:26:26Z

My main thought is that this API would feel much more natural on a Dataset object, alongside a .plot.scatter() method.

That said, I suppose this could still be useful and I don't think it's harmful to expand the API here. It does feel a little strange that if you had a DataArray with non-dimension coordinates you could make a plot without including any of the DataArray values, e.g., xr.DataArray(..., dims=['x'], coords={'x': ..., 'y': ('x', ...)}, name='f').plot.line(x='x', y='y').

dcherian · 2018-02-21T17:05:37Z

either by (i) specifying the name of the variable to the axis you want to plot it onto, or (ii) by specifying the name of the coordinate you want to use for the axis. Since (ii) is the default and only option for 1D and 2D plots until now, I just wondered if (i) is very necessary.

It does feel a little strange that if you had a DataArray with non-dimension coordinates you could make a plot without including any of the DataArray values

Good points. I'll change it so that only one of x and y can be specified.

My main thought is that this API would feel much more natural on a Dataset object, alongside a .plot.scatter() method.

It's very useful in oceanography (and meteorology) where we want to make plots of physical quantities like temperature against depth; it is much more natural to see depth on the y-axis than the x-axis. This is the original usecase @rabernat mention in #575.

The Dataset API is a more involved undertaking that I'm not confident of executing at this point.

stickler-ci · 2018-02-21T17:38:56Z

xarray/plot/plot.py

    add_legend = kwargs.pop('add_legend', True)

    ax = get_axis(figsize, size, aspect, ax)

+    error_msg = 'must be either None or %r' % (' or '.join(darray.dims))
+
+    if x not in [None, *darray.dims]:


E999 SyntaxError: invalid syntax

stickler-ci · 2018-02-21T17:49:21Z

xarray/plot/plot.py

    add_legend = kwargs.pop('add_legend', True)

    ax = get_axis(figsize, size, aspect, ax)

+    error_msg = 'must be either None or one of %r' % list(darray.dims)
+
+    if x not in [None, *darray.dims]:


E999 SyntaxError: invalid syntax

I don't know what's wrong here. It runs locally; the tests pass and flake8 goes through plot.py without errors. Is it a python2 vs python3 thing?

shoyer · 2018-02-21T17:59:17Z

Yes, this is not valid syntax on Python 2.

…

On Wed, Feb 21, 2018 at 9:53 AM Deepak Cherian ***@***.***> wrote: ***@***.**** commented on this pull request. ------------------------------ In xarray/plot/plot.py <#1926 (comment)>: > add_legend = kwargs.pop('add_legend', True) ax = get_axis(figsize, size, aspect, ax) + error_msg = 'must be either None or one of %r' % list(darray.dims) + + if x not in [None, *darray.dims]: I don't know what's wrong here. It runs locally; the tests pass and flake8 goes through plot.py without errors. Is it a python2 vs python3 thing? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1926 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABKS1pXVXGKhgmkR8yP3epLPvqZCXNipks5tXFgpgaJpZM4SLdeS> .

stickler-ci · 2018-02-21T18:14:54Z

xarray/plot/plot.py

+    error_msg = ('must be either None or one of ({0:s})'
+                 .format(', '.join(['\''+dd+'\'' for dd in darray.dims])))
+
+    if x not in [None, *darray.dims]:


E999 SyntaxError: invalid syntax

stickler-ci · 2018-02-27T06:16:28Z

xarray/tests/test_plot.py

+
+        for aa, (x, y) in enumerate(xy):
+            da.plot(x=x, y=y, ax=ax.flat[aa])
+            ax.flat[aa].set_title('x=' + str(x) + ' | '+'y='+str(y))


E226 missing whitespace around arithmetic operator

dcherian · 2018-02-27T06:20:50Z

Updated and rebased. Now these are the only options.

fmaussion · 2018-02-27T21:29:20Z

Thanks! In view of @shoyer ' comment we could revisit the API for datasets at a later stage.

shoyer · 2018-03-01T03:18:28Z

xarray/plot/plot.py

    add_legend = kwargs.pop('add_legend', True)

    ax = get_axis(figsize, size, aspect, ax)

+    error_msg = ('must be either None or one of ({0:s})'
+                 .format(', '.join(['\'' + dd + '\'' for dd in darray.dims])))


just use repr(dd) here instead of '\'' + dd + '\''

shoyer · 2018-03-01T03:18:49Z

xarray/plot/plot.py

+        raise ValueError('y ' + error_msg)
+
+    if x is not None and y is not None:
+        raise ValueError('You cannot specify both x and y kwargs.')


This should probably be qualified by "for line plots"

Supports both 1D and 2D DataArrays as input. Change variable names to make code clearer: 1. set xplt, yplt to be values that are passed to ax.plot() 2. xlabel, ylabel are axes labels 3. xdim, ydim are dimension names

dcherian · 2018-03-01T04:01:59Z

Done and rebased on master.

shoyer · 2018-03-01T04:43:19Z

xarray/plot/plot.py

+        Coordinate for which you want multiple lines plotted
+        (2D DataArrays only).
+    x, y : string, optional
+        Coordinates for x, y axis. Only one of these may be specified.


This should probably say something like "The other coordinate plots values from the DataArray on which this plot method is called."

shoyer · 2018-03-01T04:45:14Z

xarray/tests/test_plot.py

+
+        for aa, (x, y) in enumerate(xy):
+            da.plot(x=x, y=y, ax=ax.flat[aa])
+            ax.flat[aa].set_title('x=' + str(x) + ' | ' + 'y=' + str(y))


Is there any point to this line?

No. I copied the test over from my debugging plots. I'll remove it (I assume you mean the set_title bit).

shoyer · 2018-03-01T04:45:39Z

xarray/tests/test_plot.py

+              [None, 'z'],
+              ['z', None]]
+
+        f, ax = plt.subplots(2, 4)


You only have two cases now, so no need for 2x4 subplots.

shoyer · 2018-03-03T19:39:30Z

@fmaussion any further concerns here? This looks good to me.

fmaussion · 2018-03-05T22:15:09Z

Thanks @dcherian ! This is a nice feature

stickler-ci reviewed Feb 20, 2018

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dcherian force-pushed the line-specify-xy branch from e57b452 to 87bb820 Compare February 20, 2018 06:10

fmaussion reviewed Feb 20, 2018

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stickler-ci reviewed Feb 21, 2018

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dcherian force-pushed the line-specify-xy branch from 9e75869 to fabdc04 Compare February 27, 2018 06:16

stickler-ci reviewed Feb 27, 2018

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shoyer reviewed Mar 1, 2018

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dcherian added 2 commits February 28, 2018 19:59

Add x,y kwargs for plot.line().

d404cea

Supports both 1D and 2D DataArrays as input. Change variable names to make code clearer: 1. set xplt, yplt to be values that are passed to ax.plot() 2. xlabel, ylabel are axes labels 3. xdim, ydim are dimension names

Respond to comments.

c1d7135

dcherian force-pushed the line-specify-xy branch from 01153d2 to ab1431f Compare March 1, 2018 04:00

dcherian added 3 commits February 28, 2018 20:01

Only allow one of x or y to be specified.

2bf23f5

fix docs

81f5a65

Follow suggestions.

3cd49cb

dcherian force-pushed the line-specify-xy branch from ab1431f to 3cd49cb Compare March 1, 2018 04:01

shoyer reviewed Mar 1, 2018

View reviewed changes

Follow suggestions.

cf25260

fmaussion merged commit 4983f1f into pydata:master Mar 5, 2018

dcherian deleted the line-specify-xy branch May 10, 2018 05:12

TomNicholas mentioned this pull request Jan 29, 2019

Line plot with x=coord putting wrong variables on axes #2725

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Add x,y kwargs for plot.line(). #1926

Add x,y kwargs for plot.line(). #1926

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Add x,y kwargs for plot.line(). #1926

Add x,y kwargs for plot.line(). #1926

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dcherian commented Feb 20, 2018 • edited Loading

Description

Example

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