What is fold change? What is logFC (log fold change)?
What is fold change?
Fold change is a metric that expresses the extent of change between two measurements. In gene expression analysis, such as microarray or RNA-Seq analysis, it represents the ratio of expression levels between different samples or groups.
What is logFC (log fold change)?
Fold change is often converted to a logarithmic scale. This converted value is called log fold change (logFC, log2 fold change). In many cases, the base used is 2.
Examples of Fold Change / logFC
For example, if the average expression level is 100 in the control group and 200 in the treatment group, the fold change is 2, and the logFC is 1.
| Gene Name | Average Expression Level in the Control Group | Average Expression Level in the Treatment Group | fold change | logFC |
| Gene A | 100 | 200 | 2 | 1 |
| Gene B | 100 | 400 | 4 | 2 |
| Gene C | 200 | 100 | 0.5 | -1 |
In gene expression analysis, such as microarray or RNA-Seq analysis, figures such as Volcano plots and MA plots are commonly drawn. LogFC corresponds to the x-axis in a Volcano plot and to the y-axis in an MA plot.
Example of a Volcano Plot
Example of an MA Plot
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