# Documentation

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# lsline

Add least-squares line to scatter plot

## Syntax

```lsline lsline(ax) h = lsline(___) ```

## Description

`lsline` superimposes a least-squares line on each scatter plot in the current axes. Scatter plots are produced by the MATLAB® `scatter` and `plot` functions. Data points connected with solid, dashed, or dash-dot lines (`'-'`, `'--'`, or `'.-'`) are not considered to be scatter plots by `lsline`, and are ignored.

`lsline(ax)` superimposes a least-squares line on the scatter plot in axis `ax`.

`h = lsline(___)` returns a column vector of handles `h` to the least-squares lines, using any of the previous syntaxes.

## Examples

collapse all

Generate three sets of sample data and plot on the same figure.

```x = 1:10; rng default; % For reproducibility figure; y1 = x + randn(1,10); scatter(x,y1,25,'b','*') hold on y2 = 2*x + randn(1,10); plot(x,y2,'mo') y3 = 3*x + randn(1,10); plot(x,y3,'rx:') ```

Add a least-squares line for each set of sample data.

```lsline ```

Define the x-variable and two different y-variables to use for the plots.

```rng default % For reproducibility x = 1:10; y1 = x + randn(1,10); y2 = 2*x + randn(1,10); ```

Define `ax1` as the top half of the figure, and `ax2` as the bottom half of the figure. Create the first scatter plot on the top axis using `y1`, and the second scatter plot on the bottom axis using `y2`.

```figure ax1 = subplot(2,1,1); ax2 = subplot(2,1,2); scatter(ax1,x,y1) scatter(ax2,x,y2) ```

Superimpose a least-squares line on the top plot, and a reference line at the mean of the `y2` values in the bottom plot.

```lsline(ax1) mu = mean(y2); refline(ax2,[0 mu]) ```