This portion of the panel allows you to select the region over which you will make
the plot.
First note that you need to have opened a data file for anything in this section
to work.
Click on Start to begin; nothing will happen until you do this. Once you have
"started"
some curves should appear on the image to the left and some new text boxes should
appear
below the Start button. If you selected your
independent/dependent variables to be Qx/Qy or Qy/Qx you
will get a
rectangle. If you chose Line you will get a line segment. If the dependent variable is Ellipse
you will get an elllipse. Otherwise you will
get a pie-shaped wedge.
At this point, you can change the region of integration either by typing in the
appropriate
boxes or by dragging on the corners of the box or pie in the image. To drag on
the corner,
click on the large dot at one of the corners, wait until the color
changes from
blue to red, and then drag to the new position.
If all of the limits are outside of the range of the image, you might not see any lines or corners at all. In that case you should type values in the appropriate boxes until you get the region of interest visible on the false color image. The limits for the Line and Ellipse options behave somewhat differently from the others. For the Line option, the "Low" and "High" X- and Y-Pixel values are the coordinates of the two ends of the line segment. "Fract" is the equivalent of "Delta" for the other plots--the number of points will be 1 + 1/Fract. Pixels are included in the plot if they are within Width/2 of the line segment itself. So a Width of zero will in general not include any pixels at all. (The default is 3). It is suggested that for this kind of plot you will almost certainly want to Average rather than Sum the data. For the Ellipse option, the independent variable is always Chi and always goes from zero to 360; the dependent variables are the lengths of the semimajor and semiminor axes a and b (with however b being allowed to be greater than, equal to, or less than a). You also need to set the "delta"--the increment over which the independent variable is plotted. If you make it too large you will have a plot with poor resolution. If you make it too small you will end up with a noisy plot. (If you make it smaller than one pixel you will get a very strange-looking plot.) Also, there is a defined limit on the maximum number of data points, currently set at 2000. Note that if you are going make plots of a number of related data sets, you probably want to set the integration region and the delta to be the same for each data set. Very important: when you are finished setting the region, click on Done. Otherwise, the mouse will still be enabled to set the integration region, and you will get confusing results in other parts of the program. |