Text and Annotation

Text and Annotation

• When drawing large and complex plots in Matplotlib, we need a way of labelling certain portion or points of interest on the graph. To do so, Matplotlib provides us with the "Annotation" feature which allows us to plot arrows and text labels on the graphs to give them more meaning.

• There are four important parameters that you must always use with annotate().

a) text: This defines the text label. Takes a string as a value.

b) xy: The place where you want your arrowhead to point to. In other words, the place you want to annotate. This is a tuple containing two values, x and y.

c) xytext: The coordinates for where you want to text to display.

d) arrowprops: A dictionary of key-value pairs which define various properties for the arrow, such as color, size and arrowhead type.

Example :

importmatplotlib.pyplot as plt

importnumpy as np

fig, ax = plt.subplots()

x = np.arange(0.0, 5.0, 0.01)

y =np.sin(2* np.pi *x)

# Annotation

ax.annotate('Local Max',

    xy = (3.3, 1),

    xytext (3, 1.8),

    arrowprops = dict(facecolor = 'green',

    shrink =0.05))

ax.set_ylim(-2, 2)

plt.plot(x, y)

plt.show()

Output:

Example :

importplotly.graph_objectsasgo

fig=go.Figure()

fig.add_trace(go.Scatter(

x=[0,1,2,3,4,5,6,7,8],

y=[0,1,3,2,4,3,4,6,5]

))

fig.add_trace(go.Scatter(

x=[0,1,2,3,4,5,6,7,8],

y=[0,4,5,1,2,2,3,4,2]

))

fig.add_annotation(x=2,y=5,

text="Text annotation with arrow",

showarrow=True,

arrowhead=1)

fig.add_annotation(x=4,y=4,

text="Text annotation without arrow",

showarrow=False,

yshift = 10)

fig.update_layout(showlegend=False)

fig.show()

Output: