QtiPlot - FAQs

Frequently Asked Questions:

1. How can I visualise data from a text file?

Go to the 'File' menu->'Import ASCII'.

2. How can I plot data from a table (worksheet)?

Click on the table header to choose the columns to plot and then right click. Chose the 'Plot' option from the pop-up menu and then the type of plot you want.
You can also use the plot assistant: press 'CTRL+ALT+W' keys to show it, or go to 'View' menu -> 'Plot wizard'.

3. How can I export a plot to an image format?

Right click in the plot window and chose the 'Export' option.

4. Can I export transparent images?

Yes, ".png" images have transparent background.

5. How can I export a text file?

Go to the 'File' menu->'Export ASCII'

6. How can I choose a window using the project explorer?

Double click on the window name will show the window maximized, even if it was hidden before.

7. How can I choose the data range from a plot curve, when doing a curve fit?

Go to the 'Data' menu->'Select data range'. Click in the plot window and use the 'Up' and 'Down' arrows keys to select the curve to analyse. Keeping 'CTRL' button and 'Left' or 'Right' arrow keys simultaneousely pressed permit to move the selected cursor and consequently to modify the data range.

8. Can I fit a plot curve using my own function?

Go to the 'Analysis' menu->'Fit Wizard...'. Define the function (myFunction=...), enter the initial guesses for the parameters, choose the fitting range and the number of iterations and click 'OK'.

9. How can I visualize a pixel line profile from an image?

Right click on the image you want to analyse and select the option 'View pixel line profile' from the popup menu. A dialog window opens and allows you to select the number of pixels used for the analysis. Choose a value and click "OK". Then click on the image to select the start point and move your mouse to select an end point while keeping the left button pressed. When you release the left button a plot window appears, representing the pixel intensity versus pixel index.

10. How can I make a graph that has one x-axis, but two y-axes with different orders of magnitude?

In QtiPlot the procedure is very simple, no need for two plot layers like in Origin. Select two columns that you want to display and plot them in the same layer. Add a right axis to the newly created plot layer, via the "Format | Axes" dialog. Double-click on the plot and from the pop-up dialog select one of the two curves. Go to the "Axes" tab of the dialog and from the "y Axes" box, select "Right" and click apply. It's done!

If the two columns containing the data you want to display belong to the same table, it's even easier: just select them and go to the "Plot | Special Line/Symbol | Double-Y" menu.