# Documentation

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## Creating Plots with Two y-Axes

This example shows how to create and customize plots with two y-axes.

### The `yyaxis` Function

When analyzing relationships between variables, it can be useful to create a line plot with two y-axes. For example, create vectors for precipitation and temperature for each month.

```monthnum = 1:12; precip = [3.4 3.3 4.3 3.7 3.5 3.7 ... 3.4 3.4 3.4 3.9 4.0 3.8]; temp = [16 25 40 48 59 70 ... 77 77 65 56 47 34];```

Use the `yyaxis left` command to create an axis with a y-axis on both the left and right sides. Subsequent plotting commands use the left y-axis.

```figure yyaxis left plot(monthnum,precip) xlabel('Month') ylabel('Precipitation') title('Monthly Climate Data')```

Create a line plot for the temperature of each month using the y-axis on the right. The `yyaxis` `right` command activates the right y-axis.

```yyaxis right plot(monthnum,temp) ylabel('Temperature')```

### Add Multiple Lines to Plot With Two y-Axes

To add multiple lines to the plot, use the `hold on` command followed by additional plot commands. The additional lines use the same color as the right y-axis and cycle through the line style order.

```low = [22 25 31 41 50 60 ... 65 65 57 47 38 28]; high = [36 39 45 56 66 76 ... 81 80 72 61 51 41]; hold on plot(monthnum,low) plot(monthnum,high) ylabel('Temperature') legend('Precipitation','Temperature','Low','High') hold off```

### Combining Visualization Types With Two y-Axes

With yyaxis, you can use a different plot type on each y-axis. For example, create a bar chart of precipitation by month.

```clf bar(monthnum,precip,'FaceColor','g') xlabel('Month') ylabel('Precipitation') title('Monthly Climate Data')```

You can add a right y-axis to an existing chart with the `yyaxis right` command. The right y-axis uses the next color in the color order for the axes.

```yyaxis right plot(monthnum,temp) ylabel('Temperature')```

To adjust the limits of the left y-axis, use the `yyaxis left` command to activate the left side and then set the limits.

```yyaxis left ylim([0 5]) xlim([0 13])```