Researchers will wish to visualize their data in order to compare the hybridization signals for the probes recognizing the different pathogen signatures. DetectiV provides a function called show.barplot for this. The output from prepare.data is passed to the function, along with the name of the column containing the variable by which the data will be grouped, referred to here as group. An example in pathogen detection data may be species, genus, family, and so on. The data are sorted into unique groups as defined by the unique values of group. A barplot is drawn, with one bar per unique probe. Probes from the same group are drawn together. Each group is represented by a unique background color, enabling the user to easily visualize the different groups. An example output is shown in Figure 2 . This sample comes from Urisman et al [9] and represents data from a virus detection microarray hybridized with amplified RNA from nasal lavage, positive for respiratory syncytial virus by direct fluorescent antibody (DFA) test. The group chosen here is virus family. It is quite clear from this image that there is a virus from the family Paramyxoviridae present in the sample, demonstrated by the high bars associated with that family.