Download Melanie 3 User Manual - Bio-Rad

SCATTER PLOT
Analyze
Scatters Plot
Select two or more gels and groups of spots. Choose Scatter Plot. Select one of
the spot value types (Od, Vol, Area, %Od, %Vol) to calculate the correlation. The
Scatter Plot window plots the pairs values, and the fitting line of each selected gel
against the reference gel (Fig. 7-2).
Reports
Regression
line
Regression
line equation
Correlation coefficient
Number of pairs
Figure 7-2. Scatter graphic on groups.
As usual, you may save and print the graphics using the corresponding buttons of
the window toolbar.
The relationship between the spots values from two gels can be estimated by
searching the linear dependence between the spot values from one gel against the
values taken in the other gel. The linear dependence is defined as the best fitting
straight line through the pair values. The fitting line is defined by a slope and its offset, i.e. the equation y = s lope ⋅ x + offset . In Melanie’s case, variable x is the spot
values from one gel and y is the corresponding value in the reference gel.
The goodness-of-fit of this approximation is given by the correlation coefficient Corr.
This coefficient can vary between -1 and +1, where an absolute value near 1 indicates a good fit (i.e the spot values of one gel can be predicted, to some extent, by
the values of the other gel) while a low value indicates that the data could not be
approximated by a straight line.
For example:
• 1.0 ⋅ x + 0 with 1 correlation indicates that all paired spot values are the
same in the two gels.
• 1.2 ⋅ x + 0 with 0.95 correlation indicates that almost all paired values are
20% higher in the reference gel.
Melanie 3 User Manual
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