The following overview on plot Resolution applies to:

•Histograms

•Kinetics plots

•Dot plots and Color Dot plots

•Density plots and Contour plots

•Surface Plots

 

 

What is the resolution of a plot?

 

The resolution of a plot is the number of bins (channels) that data for each parameter is subdivided into. Before displaying a plot, FCS Express assesses the data and places events into the number of bins selected by the user. The process is known as binning. The events in each bin are displayed on the plots. When the resolution is lower, the same data gets placed into fewer bins, meaning that the number of events in each bin will be higher resulting in histograms that appear "smoother" and 2D plots that appear "blocky". Conversely, when resolution is higher, data gets placed into more bins, meaning the number of events in each bin will be lower. Resolution values are set as defaults for each plot type that are generally applicable for the majority of data sets. While decreasing the resolution may help to smooth data, you may eventually lose the overall "shape" of the data by decreasing resolution too much. While increasing resolution may reveal more dots in a 2D plot, it may also eventually reduce the ability to define the overall "shape" of the data. Additionally, increasing resolution on some plots in FCS Express may reduce performance without adding any benefit to data visualization.

 

FCS Express assesses and places data into the bins according to the scale of the data file.

 

Note: Statistics are always calculated on the full range of data, regardless of how the resolution is set on a particular plot.

 

 

In FCS Express, you can set the value of the resolution (i.e. the number of bins), and also control the resolution Minimum and Maximum that is displayed:

 

•Plot Resolution

 

oFor histograms (Figure 5.52) it can be customized in the Formatting dialog Histogram Specific Options category. You can set the resolution to a specific number chosen from the Plot resolution drop-down list.

 

 

 

oFor 2D plots (Figure 5.53) it can be customized in the Formatting dialog Binned Dot (or Plot) Specific Options category. You can set the resolution from the Resolution drop-down list (32 x 32 to 1024 x 1024).

 

 

 

 

•Min/Max (Resolution)

 

Min/Max Resolution can be found in the Axes Formatting dialog.

FCS Express gives you the option of dividing the full range of data into the resolution (number of bins) you specify, or to "cut out" either the top end or the low end of the data. By doing this the Plot Resolution is basically applied to the displayed range, rather than to the entire .fcs file.

In most cases, it is preferable to leave the resolution Maximum and Minimum at the default value, i.e., Automatic. However, there are two reasons you might want to manually set the Minimum or Maximum on a plot axis.

 

1. In certain cases, some instruments may store outlier values in the data. In general, outliers will simply represent noise, not significant data. If an outlier data point is included when the plot is calculated, information may be lost in a significant part of the range. In this case, you can exclude the extreme data point by setting a minimum or maximum value to use for significant data points.

 

2. You may want to set the Minimum and/or Maximum to provide detailed zooming into a small range of values.

 

 

 

 

Technical note: Axis Resolution and Statistics

 

In FCS Express, all the statistics are calculated on the raw data, irrespective of the display scaling. However, when Gates and Quadrants are created, decisions must be made in cases when an event falls on the line of the gate or quadrant.

 

In FCS Express, Gates and Quadrants are calculated and drawn in a binned space with binning dependent on both the Scaling and the Resolution Minimum/Maximum of the plot. In turn, the inclusion or exclusion of an event on the border line of a gate or in a quadrant is highly dependent on the scaling of the plot, and on the Resolution Minimum/Maximum, of the plot the Gate/Quadrants was drawn on.

 

When adjustments to the scaling or resolution of a plot are made, an event may then fall to a different side of the border line of the gate/quadrant, and the user may notice very slight changes in the statistics of gated events which are usually minimal and make no impact on the interpretation of the results.

 

Please refer to the Axis Scale and Statistics chapter for more details.