linkdata

Automatically update charted data

Description

Use data linking to synchronize charts and their workspace variables. Linked charts automatically update with changes to workspace variables, and workspace variables automatically update with chart modifications made via the brush tool.

Link charts and workspace variables using the linkdata function or by selecting the Link Plot button from the figure toolbar.

Creation

Syntax

linkdata on

linkdata off

linkdata

linkdata showdialog

linkdata(fig,___)

l = linkdata

l = linkdata(fig)

Description

linkdata on turns on data linking mode for the current axes.

linkdata off turns off data linking mode.

linkdata toggles the data linking mode between 'on' and 'off'.

linkdata showdialog opens the Linked Plot Data Sources dialog box. Use this syntax to interactively synchronize a chart with workspace variables.

linkdata(fig,___) specifies the data linking mode for the specified figure. Use single or double quotation marks around the options 'on' and 'off'. For example, linkdata(fig,'on').

l = linkdata creates a LinkData object. This syntax is useful for querying the data linking mode.

l = linkdata(fig) creates a LinkData object for the specified figure.

Input Arguments

fig — Target figure

Figure object

Target figure, specified as a Figure object. If you do not specify the figure, then data linking is enabled or disabled for the current figure.

Properties

Enable — Data linking mode

'off' (default) | 'on'

This property is read-only.

Data linking mode, specified as 'off' or 'on'.

Examples

Update Chart When Workspace Variables Change

Create a bar chart and enable data linking. Data linking synchronizes the bar chart with the x and y variables in the workspace.

x = linspace(-5,5,11);
y = abs(x);
bar(x,y)
linkdata on

Modify one of the values in y. Note that the bar chart immediately updates to reflect the change.

y(6) = 4;

Update Workspace Data When Chart Changes

Interactively delete workspace values by selecting them in a chart, using linkdata and the brush tool.

Create some data to plot. Note that x and y contain 21 values.

x = linspace(-5,5,21);
y = -abs(x);

lengthX = length(x)
lengthY = length(y)

lengthX =

    21


lengthY =

    21

Plot the data, then enable both data linking and brushing.

scatter(x,y,'filled')
linkdata on
brush on

Highlight the data values you want to delete. To remove the brushed data from the chart, right-click on a brushed value and select Remove from the context menu.

The chart is linked to its data sources, so deleting values from the chart also deletes them from the data sources. Note that x and y now contain only 14 data values.

lengthX = length(x)
lengthY = length(y)

lengthX =

    14


lengthY =

    14

Link Complex Data

Use data linking with complex numbers. When you plot complex data, the real and imaginary parts of the data do not correspond to different workspace variables. As a result, the linkdata function cannot identify data sources for the x- and y-axes. To link complex data, you must manually specify the real part of the complex data as the x-component and the imaginary part as the y-component.

First, create a matrix of complex data values and plot them. Then, open the Linked Plot Data Sources dialog box by calling linkdata showdialog.

z = eig(randn(20,20));
plot(z)
linkdata showdialog

Manually specify the real and imaginary parts of the data by typing real(z) and imag(z) in the text boxes under X and Y.

Now the chart is linked to its data sources. If you change z, then the plot will update to reflect the new data.

To avoid using the dialog box, you can specify the data sources when first plotting the data values.

z = eig(randn(20,20));
plot(z,'XDataSource','real(z)','YDataSource','imag(z)')
linkdata on

Tips

• If linkdata cannot unambiguously identify data sources for a chart, then the chart will not synchronize with workspace variables. If you call linkdata and your chart does not update when you change a variable, then open the Linked Plot Data Sources dialog box by calling linkdata showdialog and manually link the chart to its data sources.

• The linkdata function updates linked data sources and charts around twice a second. To smoothly animate changes in data values, create loops that execute two times per second or less. For more information, see the pause function.

• Once a chart is synchronized with its workspace variables, programmatic changes to the data properties of the chart (for example, XData) do not update the workspace variables. Workspace variables only update when you modify plotted data interactively, using the brush tool.

Algorithms

Data linking connects a chart and its workspace variables using the chart's data source properties (for example, XDataSource). When you turn on data linking for a figure, MATLAB^® compares variables in the workspace to plotted data in the figure. When it finds a match, MATLAB assigns that variable to the appropriate data source property of the chart.

Version History

Introduced in R2008a