A histogram shows a distribution of a set of values. Histograms are often used for examining and comparing distributions, e.g. of expression values of different samples, in the quality control step of an analysis. You can create a histogram showing the distribution of expression value for a sample:

        Toolbox | Microarray Analysis (Image expressionfolder)| General Plots (Image general_plots_folder_closed_16_n_p) | Create Histogram (Image histogram)

Select a number of samples ( (Image array), (Image rnaseq), (Image rnaseqtrack_16_h_p)) or a graph track. When you have selected more than one sample, a histogram will be created for each one. Clicking Next will display a dialog as shown in figure 31.57.

Image histogram_step2
Figure 31.57: Selecting which values the histogram should be based on.

In this dialog, you select the values to be used for creating the histogram (see Selecting transformed and normalized values for analysis).

Click Finish to start the tool.