matplotlib.pyplot.fill_betweenx

matplotlib.pyplot.fill_betweenx(y, x1, x2=0, where=None, step=None, interpolate=False, *, data=None, **kwargs) [source]

Fill the area between two vertical curves.

The curves are defined by the points (x1, y) and (x2, y). This creates one or multiple polygons describing the filled area.

You may exclude some vertical sections from filling using where.

By default, the edges connect the given points directly. Use step if the filling should be a step function, i.e. constant in between y.

Parameters:

yarray (length N)

The y coordinates of the nodes defining the curves.

x1array (length N) or scalar

The x coordinates of the nodes defining the first curve.

x2array (length N) or scalar, optional, default: 0

The x coordinates of the nodes defining the second curve.

wherearray of bool (length N), optional, default: None

Define where to exclude some vertical regions from being filled. The filled regions are defined by the coordinates y[where]. More precisely, fill between y[i] and y[i+1] if where[i] and where[i+1]. Note that this definition implies that an isolated True value between two False values in where will not result in filling. Both sides of the True position remain unfilled due to the adjacent False values.

interpolatebool, optional

This option is only relevant if where is used and the two curves are crossing each other.

Semantically, where is often used for x1 > x2 or similar. By default, the nodes of the polygon defining the filled region will only be placed at the positions in the y array. Such a polygon cannot describe the above semantics close to the intersection. The y-sections containing the intersection are simply clipped.

Setting interpolate to True will calculate the actual intersection point and extend the filled region up to this point.

step{'pre', 'post', 'mid'}, optional

Define step if the filling should be a step function, i.e. constant in between y. The value determines where the step will occur:

'pre': The y value is continued constantly to the left from every x position, i.e. the interval (x[i-1], x[i]] has the value y[i].
'post': The y value is continued constantly to the right from every x position, i.e. the interval [x[i], x[i+1]) has the value y[i].
'mid': Steps occur half-way between the x positions.

Returns:

PolyCollection: A PolyCollection containing the plotted polygons.

Other Parameters:

**kwargs

All other keyword arguments are passed on to PolyCollection. They control the Polygon properties:

Property	Description
`agg_filter`	a filter function, which takes a (m, n, 3) float array and a dpi value, and returns a (m, n, 3) array
`alpha`	float or None
`animated`	bool
`antialiased` or aa or antialiaseds	bool or sequence of bools
`array`	ndarray
`capstyle`	{'butt', 'round', 'projecting'}
`clim`	(vmin: float, vmax: float)
`clip_box`	`Bbox`
`clip_on`	bool
`clip_path`	Patch or (Path, Transform) or None
`cmap`	colormap or registered colormap name
`color`	color or sequence of rgba tuples
`contains`	callable
`edgecolor` or ec or edgecolors	color or sequence of colors or 'face'
`facecolor` or facecolors or fc	color or sequence of colors
`figure`	`Figure`
`gid`	str
`hatch`	{'/', '\', '\|', '-', '+', 'x', 'o', 'O', '.', '*'}
`in_layout`	bool
`joinstyle`	{'miter', 'round', 'bevel'}
`label`	object
`linestyle` or dashes or linestyles or ls	{'-', '--', '-.', ':', '', (offset, on-off-seq), ...}
`linewidth` or linewidths or lw	float or sequence of floats
`norm`	`Normalize`
`offset_position`	{'screen', 'data'}
`offsets`	array-like (N, 2) or (2,)
`path_effects`	`AbstractPathEffect`
`picker`	None or bool or float or callable
`pickradius`	unknown
`rasterized`	bool or None
`sketch_params`	(scale: float, length: float, randomness: float)
`snap`	bool or None
`transform`	`Transform`
`url`	str
`urls`	List[str] or None
`visible`	bool
`zorder`	float

Notes

Note

In addition to the above described arguments, this function can take a data keyword argument. If such a data argument is given, the following arguments are replaced by data[<arg>]:

All arguments with the following names: 'where', 'x1', 'x2', 'y'.

Objects passed as data must support item access (data[<arg>]) and membership test (<arg> in data).