Fig. 2

Example for a heatmap, which is a data representation in the form of a map in which data values are color coded. Here, sequencing data from the 1000 genomes project [30] are visualized. Rows correspond to samples and are ordered by processing date, and columns represent genome location of the corresponding sequence. One can see that for the dates 243–254, orange color indicating high values is overrepresented, compared to blue color indicating low values. This demonstrates that so-called batch effects are present, i.e. systematic biases in the data, which are discussed in detail in section “IDA3.2: Batch correction.” Source for the data: [29]