FlowJo v9 Manual


Why do you need to transform the data display?

When data is properly compensated, it is common that a large number of cells are displayed squished against the axis. The cells become piled up in the first channel (against the axis) because the fluorescence parameters are displayed on a log scale where it is not possible to display "zero" or negative values. These negative values occur as a result of measurement error (not as a result of compensation). The spreading of a population into the negative is the result of measurement error that is inherent in the data we collect on flow cytometers. Even though the measurement error is the same in uncompensated samples, the error becomes obvious in the low regions of the log scale because log scales expand the view of data in the lower regions (frist decade) and compress the view of data in the upper regions (fourth decade).

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