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FlowJo draws only one type of contour
plot, using equal probability contouring. This algorithm generates,
in general, graphs which are most accurately interpreted by our brains,
in terms of relatively frequencies of subpopulations. All contouring
algorithms have advantages and disadvantages, but probability contouring
is probably the most informative. Combined with the display of outliers,
this generates an extremely informative graphic that does not over-emphasize
narrow peaks nor hide low-frequency information. There
are several options available in drawing the plots (available from
the menu). These include the option
of drawing "2%", "5%" or "10%" contour
plots, "smoothed" or not, and "outliers" or
not. Contrary to the belief of many people, smoothing does not alter
the data nor does it distort it. Thus, it is by default left on.
Note that turning smoothing off can cause the program to take much
longer to draw the plots. "Show Outliers" controls whether
events falling outside of the lowest contour are drawn with dots--thus,
combining the best advantages of dot plots (revealing low-frequency
data) with the best of contour plots (allow high-frequency data
to be accurately displayed). 2%, 5% and 10% plots have 50, 20, and
10 contour lines (respectively) that are distributed so that the
same number of cells fall between each pair of contour lines.
The first set of graphs below compares the same
data using different contouring thresholds. The second set of graphs
compares 5% probability plots with different options.
You may view a comparison
of all the bivariate displays for this
same data. |
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