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Keywords: Graphing Software, graphing, software, graphing
SigmaPlot Graphing Software
...add error bars, including asymmetric error bars
Error bars are one of the most powerful features of SigmaPlot. There are also many ways to create error bars.
To create an error bar plot, select one of the error bar graph types. Your error bar computation choices are made from the graph wizard.
Computing error bars from data statistics
SigmaPlot is powerful at summarizing your raw data, so you don't have to compute your means and std.
deviations or errors - SigmaPlot will do that for you. Just leave your data in the raw format and choose any of the options from Columns Means or below from the Symbol Value drop down list.
If your data repetitions are arranged along rows rather than down columns, select one of the rowwise options. This is the option you generally select if you
are computing error bars for a grouped bar chart from raw data. You can also create grouped bar chart data from "By Category" data which is the typical data format for statistical datasets.
Once you've selected your symbol value, you can now select the computations for the upper and lower error bars.
Using raw data is particularly important if you plan on curve fitting this data later. SigmaPlot automatically uses all your data (rather than just the mean) to
perform the curve fit, which produces more accurate results.
Plotting values as symmetric error bars
To plot values in a worksheet column as your corresponding error bar values,
select the Worksheet Columns option. You will then be prompted to pick the worksheet column for the error bar values when picking your data to plot.
Plotting values as asymmetric error bars
Asymmetric error bars can be computed from raw data simply by selecting
different computations for the upper and lower error bars. However, if you have your error bar data in multiple columns, you will need to select the "Asymmetric Error Bar Columns" option.
NOTE: Asymmetric error bar values are plotted as the absolute value of the error bar data; that is, if you use a datapoint value of 6, and you want the error
bars to be drawn to 1.2 above and 0.4 below the data point, your error bar values need to be 7.2 and 5.6.
Using Offset Values
If your values are currently offsets and not absolute values, you can easily transform your data using Quick Transform.
- Press shift+F10 to open the Quick Transforms palette. Click the left box and click an empty column, then click the right box.
- Click the data point column, type "+" (or click the "+" button), then click the upper error bar offset column. Click Run.
- Now click the left box again, click the column next to the first transformed column, then click the right box.
- Click the data point column, type "-" click the "-" button), then click the lower error bar offset column. Click Run.
Note that when picking your data to plot, you will be prompted to select only one error bar column. Click the transformed column for the upper error bars. The adjacent column is automatically assumed.
Back to SigmaPlot FAQ's Page.
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