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Add graphs and charts to your Visual FoxPro applications

A free download which takes the hard work out of charting in VFP

If you want an easy way of creating charts and graphs for your Visual FoxPro application, take a look at our SimpleChart control. Download the control from our web site, add it to your forms, adjust a few properties, and before you know it you will be producing good-looking line graphs, histograms, pie charts and a dozen other two- and three-dimensional charts.

What is it?

SimpleChart is essentially a wrapper for Microsoft's MSChart ActiveX control, which comes free with Visual FoxPro (versions 6.0 and above). If you've ever used MSChart, you'll know that it can produce a wide range of useful charts, but it can hardly be described as programmer-friendly. Getting the data into the chart is hard enough. You also have to get to grips with a confusing array of properties and methods in order to customise the appearance of the chart.

The SimpleChart control aims to take the hard work out of using MSChart. As a minimum, you only have to provide a table or cursor for the data, set two properties of the control and call a single method.

SimpleChart is free. To download it, see the instructions at end of this article.

Start with a cursor

The first step in using SimpleChart is to get the data into a table or cursor. Essentially, this should contain one field for each of the series to be plotted, plus, optionally, a further field to hold the row labels. Each record in the cursor should correspond to one data point. (Although we will use the term cursor from now, you could just as well use a physical table.)

For example, let's suppose you want to plot monthly sales values and monthly sales quantities for a given year. Your cursor might look something like this:

This will produce a chart with two lines and twelve data points, with the horizontal axis showing the twelve month names (Figure 1). If you want to plot additional series along the same axes, just add further fields to the cursor.

Figure 1: A simple chart showing two time series

Properties and methods

The next step is to drop the SimpleChart control onto a form, and to adjust two of its properties. You can do this either in the Form Designer or at a suitable point in your code. A good place to write the code would be in the control's Init event.

The properties in question are:

• cAlias. Set this to the alias of the cursor containing the data to be plotted.
• cData. Set this to a comma-delimited list of the fields within the cursor which contain the data to be plotted. These fields must be numeric data types.

So to continue with the above example, if the alias of the cursor is csrSales, you might write the following code in the control's Init event:

THIS.cAlias = "csrSales"
THIS.cData = "SALES_VAL,SALES_QTY"

Finally, call the control's CreateChart method to create the chart and make it visible on the form, like so:

THIS.CreateChart

You don't need to pass any parameters to the CreateChart method. The only constraint is that the cursor or table must be open before you call it.

Customisation

The chart thus produced will be a simple two-dimensional line series, similar to the one shown in Figure 1. By default, there will be no legend or titles, and the x-axis will show default labels. Fortunately, it is easy to display other chart types and to customise their appearance in various ways.

To achieve this, adjust any or all of the properties listed below. You would normally do this before you call the CreateChart method for the first time. If you want to change any of these properties after you have displayed the chart, just call CreateChart again to make the changes visible.

• BorderStyle. The border for the entire chart (0 = no border, 1 = single line; default 0).
• cColours. A comma-delimited list of the colours to be used for the chart. The following colours are supported: red, green, blue, black, white, grey (or gray), yellow, brown, magenta, cyan, darkblue, darkgreen. For example, if the chart has three series, the following code will set these to blue, white and yellow respectively:

  THIS.cColours = "BLUE,WHITE,YELLOW"

  (These are not case-sensitive.)
• ChartType. The type of chart or graph. The following values are available: 0 = 3D bar, 1 = 2D bar, 2 = 3D line, 3 = 2D line, 4 = 3D area, 5 = 2D area, 6 = 3D step, 7 = 2D step, 8 = 3D combination, 9 = 2D combination, 14 = 2D pie, 16 = 2D XY (default: 3).
• cFootnote. Text of a small title which appears at the bottom of the chart.
• cLabels. A comma-delimited list of the labels that are to appear in the legend (if any).
• cRowLabels. The name of the field within the cursor containing the row labels. These will appear along the x-axis.
• cTitle. Text of a main title for the chart. This will appear centred at the top of the chart.
• lIgnoreZero. If .T., any zero values in the data will not be plotted (default: .F.).
• lShowMarkers. If T., data points will be highlighted by special symbols (default: .F.).
• ShowLegend. T. to show a legend (default: .F.).

All of the above properties take sensible defaults, so you can ignore any that you are not interested in.

Things that can go wrong

SimpleChart performs a minimum of error checking. The CreateChart method performs the following checks:

• A table or cursor must be specified in cAlias.
• This table or cursor must be open when you call CreateChart.
• The cData property must contain the name of at least one of the fields from the cursor.

If any of these checks fails, CreateChart will return .F. and the chart will not be created. If all is well, the method will return .T.

MSChart support

In July 1999, Microsoft announced that it would no longer support the MSChart ActiveX control within Internet Explorer. This is because the control is single-threaded and is therefore incompatible with Internet Explorer 4.0 and above.

Don't worry. This does not affect the use of MSChart within VFP. The control works happily in desktop applications.

How to download SimpleChart

Click the link below to download SIMPLECHART.ZIP. This zip file contains a class library, which in turn contains the control. The control includes a Documentation method which gives brief instructions for using the control. The total download size is a mere 9 KB.

Download now

We hope you find the control useful. Please let us have your feedback (see our Contacts page).

Note added July 2002: More information about SimpleChart is available in a new Foxstuff article, SimpleChart revisited.

Mike Lewis Consultants Ltd. March 2002. Revised November 2003 and January 2006.