## Description

#### Axes labels and legends

Here we will be placing a legend and axes labels on the graph of the function

(1)A legend is generated by setting `legend_label` when creating the plot object, and axes labels are set with the `.axes_labels()` method.

## Sage Cell

#### Code

```
p = plot(sin(pi*x), -pi, pi, legend_label='$f(x) = \sin(\pi x)$' )
p.axes_labels(['$x$', '$y = f(x)$'])
p.show()
```

## Options

#### The six gridline options

Sage has to parameters which control gridlines on graphs; `frame`, which can be set to `true` or `false` and `gridlines`, which can be set to `true`, `false`, or `minor`. Combining both, this allows for 6 different gridline options. We will demonstrate them all in the following cells. The default value of both parameters is `False`, so setting them both to `False` will produce the same graph as if you hadn't set them at all.

Adding axes labels

#### Code

`plot(x^3-x, -2, 2, gridlines=True, frame=False)`

`plot(x^3-x, -2, 2, gridlines='minor', frame=True)`

`plot(x^3-x, -2, 2, gridlines=True, frame=True)`

`plot(x^3-x, -2, 2, gridlines='minor', frame=True)`

`plot(x^3-x, -2, 2, gridlines=False, frame=False)`

`plot(x^3-x, -2, 2, gridlines=False, frame=True)`

#### Adding Arrows, Text and Points

Beyond legends and axis labels, sage also offers the ability to place arrows, points and text at specified locations using `point()`, `arrow()` and `text()`. We will be annotating the graph of

And its tangent line at $f(1)$,

(3)#### Code

```
tangent_line = plot(2*x, -2, 2, gridlines='minor')
curve = plot(x^2 + 1, -2, 2)
big_dot = point( (1,2), size=60 )
the_arrow = arrow( (0.2, 2.8), (0.9, 2.1) )
the_words = text( '$f(x) = x^2 + 1$ and tangent line at $(1, 2)$.', (0.5, -2.75), fontsize = 14 )
big_image = tangent_line + curve + big_dot + the_arrow + the_words
big_image.show()
```

A few notes on `arrow()` and `text`:

When creating an arrow, the point will be located at the second set of points; for the arrow in the graph we made, if you wanted an arrow pointing at the intersection from the opposite direction, you could input

`the_arrow = arrow( (1.8, 1.2), (1.1, 1.9))`

When using `text()`, the text will be center aligned and will originate from the point specified, so make sure to leave enough room on either side to fit what you want on the graph.

#### Graphing an Integral

Here we will use the `fill` property to graph a visualization of

#### Code

`plot(-1 + sqrt(x), 0, 2, fill=True)`

You can set the color of the filling and the transparency by setting `fillcolor` and `fillalpha`:

`plot(-1 + sqrt(x), 0, 2, fill=True, fillcolor='yellow', fillalpha=2/3)`

#### Dotted and Dashed lines

Similar to colors, you can also declare `linestyle` when creating a plot to make different patterns of dots and dashes when plotting multiple functions.

#### Code

```
P1 = plot( x^2, 0, 1.2)
P2 = plot( x^3, 0, 1.2, linestyle='-')
P3 = plot( x^4, 0, 1.2, linestyle='-.')
P4 = plot( x^5, 0, 1.2, linestyle=':')
P5 = plot( x^6, 0, 1.2, linestyle='--')
P = P1 + P2 + P3 + P4 + P5
P.show()
```

## Tags

Primary Tags—Plotting: Two-dimensional plots

Secondary Tags—Two-dimensional plots: Annotation

## Related Cells

- Plotting a Circle
- Plotting a Polygon
- Plotting an Implicit Function
- Two-Dimensional Plots
- Parametric Plots
- Line Plots
- Plotting Two-Dimensional Vector Fields
- Multiple Plots on the Same Graph
- Controlling the Viewing Window of a Plot
- Plotting Functions with Asymptotes
- Occasional Issues in Polar Plotting
- Constructing Contour Plots in Sage
- Plotting Inequalities in Sage
- Plotting Systems of Linear Inequalities
- Plotting Nonlinear Inequalities in Sage
- Making log-log Plots in Sage

## Attribute

Permalink:

Author: Gregory V. Bard. *Sage for Undergraduates.* American Mathematical Society, Providence, RI, 2015. Available at http://www.gregorybard.com/Sage.html.

Date: 27 Feb 2019 22:32

Submitted by: Zane Corbiere