 |
||||||||||||
|
||||||||||||
|
||||||||||||
|
||||||||||||
|
|
|
 |
||
| CDF, or cumulative distribution function,
plots display exactly the same information as do histograms. The difference
is that the histogram values are summed as the fluorescence intensity
increases; thus, the CDF begins at 0% (left axis) and ends at 100%
(right axis). You can change the vertical scaling
(to expand a portion of the CDF plot) by setting the appropriate fields
under the "Options" disclosure triangle at the bottom of
the plot. CDF plots are extremely useful for quickly finding the fluorescence
of a distribution corresponding to any given percentile (such as the
median). The sample plot below shows how to find the median (50th
percentile), 75th, and 90th percentiles for this data. Note that unlike
the histogram, the Y-axis is in terms of relative frequency. In this
example, the median fluorescence of the population is about 6.0 fluorescence
units.
The plot below overlays the CDF and the histogram for the same data. (This overlay was done by copying the graphs from FlowJo into Canvas and overlaying them in that program).
See also the page on histograms. |
||
