Graphs are great for understanding results in reports and papers, but to use those results in your own analysis, you'll want the underlying numerical data. Your analysis will be more flexible because you can easily include all the data from the graph, rather than just a few points read manually.

Extract numerical data from a graph in 3 steps with Dagra:

View examples of Dagra in action.

Version: 1.1.8
Updated: 11 October 2008
Size: 2.16 MB

Price: $US49.95

With Dagra, you use Bezier curves to trace the data, rather than tediously clicking on a large number of points. You simply click a point on the data, then drag to indicate the curve's tangent at that point. Usually 5-10 Bezier points are more than enough to describe even complex shapes.

Once you have layed out points to cover the data, you can tweak the Bezier data and control points so that the curve closely follows the data. Bezier curves have a long history in graphics applications like Adobe Illustrator and CorelDRAW; editing will quickly become intuitive.

Tracing data with Dagra's Bezier curves is more accurate than picking individual data points. You must decide for each point where the curve lies when picking individual data points. This can be difficult for low resolution images. In contrast, it is much easier to get a Bezier curve to match the shape of the data because you only need to adjust a few control points.

Data you trace in Dagra can be used in nearly any data analysis or plotting package. Traced data can be exported to tab- or comma-delimited text files or simply transferred using the Windows Clipboard. Add-ins for common analysis tools let you work with Dagra files directly from your favorite software.

Microsoft Excel^®

Dagra comes with a Microsoft Excel add-in letting you load data directly from Dagra documents into Microsoft Excel. The add-in places an Import Dagra File on Excel's Tools menu. When a Dagra file is opened, a new sheet is created containing the data traced.

Imported data can be used in spreadsheet calculations using the DagraEval(<sheet>, <series>, <x-value>) function, which is part of the add-in. This function returns the interpolated y-value for the given x-value.

MathCad^®

Dagra's MathCad component lets you insert Dagra data directly into your Worksheet. Dagra data can be used much the same way as values in a MathCad table component. Typically you would define a MathCad function to return values from the interpolated data.

Using values traced from data sheets lets you make MathCad worksheets that are far more flexible than if you simply entered a few selected values into your worksheet.

Mathworks Matlab^®

Matlab functions are included with Dagra to load data from documents into Matlab structures directly. You do not need to export the data to text files first. The data is stored as a set of x- and y-values that can be interpolated using Matlabs interp1 function. The following example plots the phase response of an operational amplifier:

	Data = LoadDagra('OPA27 Closed Loop Voltage Gain.dag'); F = linspace(0, 1000); Ph = interp1(Data.Phase.x, Data.Phase.y, F); figure(1); plot(F, Ph); xlabel('Frequency [Hz]'); ylabel('Phase Shift \circ'); grid on;
Data traced in Dagra can be loaded directly into Matlab. larger...

It is easy to get graphical images of data into Dagra for tracing. Many import formats formats are supported including:

• Bitmap (BMP)
• Graphic interchange format (GIF)
• Joint photographic experts group (JPG, JPEG)
• Portable network graphics (PNG)
• Tagged image format (TIF, TIFF)
• Windows meta files (WMF)
• Enhanced windows meta files (EMF)

Dagra will also import images directly from the clipboard. This is ideal for pulling graphs from Adobe Acrobat (PDF) files, a format commonly used for published papers and data sheets. Just use the Acrobat Snapshot Tool to copy the graph onto the clipboard.