Statistics versus time can be obtained by selecting 'time_series' in the menu 'ACTION'. The field must be first specified by selecting one check box on the left, for instance 'civ2'. The first field in the series is then displayed, and the question 'range of analysis OK' is asked. Answer 'No' and press the button 'set_rect' which appears on the top of the display window. Then draw a rectangle with the mouse to select a subdomain of analysis. You can manually adjust the coordinates of the four corners in the text box 'DOMAIN OF ANALYSIS', and type carriage return. Let us for instance choose [60 210 15 120], which avoids the left side of the field, perturbed by the shadow of the moving cylinder. Answer Yes to the question 'range of analysis OK' when you are satisfied. Then it is asked 'only the global statistics?'. If 'No' is answered the field inside the subdomain will be recorded in a file 'DATA/timeseries.mat' in your matlab working directory. It can be retrieved by 'matlab' using the command 'load DATA/timeseries': 'Utim' and 'Vtim' are matrices representing the set of velocity vectors versus time at position coordinates 'Xtim' and 'Ytim'. Let us answer 'Yes' to work on the statistics only.
At the end of the calculation, the mean and min max of each velocity component are plotted versus time, and a new interface 'plotgraph' appears, see Fig. 6. It allows us to plot a set of statistical quantities versus time, as well as histograms averaged over the time series (either in physical velocity or in pixel displacement). Select for instance 'Umoy','Umin', 'Umax', 'sqrt(u'2)' to give the mean x component over the domain of study versus time, the min and max and the root mean square. The check box 'pfalse' provides the proportion of false vectors removed by the Fix operation versus time.
To plot the histograms of both velocity components, select 'Uhist' and 'Vhist', and press 'PLOT'. The histogram of 'Chist', the image correlation C associated with a vector, is also of interest. Correlations close to 1 are indications of good measurements.
For leaving this session, press 'QUIT' on the 'plotgraph' interface, then it is proposed to save the results in a matlab (.mat) data file. You can then open it again with the browser of the 'plotgraph' interface, for comparison with other data. The successive curves superpose until the figure is closed. For instance in Fig. 6, the data for the first civ1 (with the pair -8|8) are compared with the refined civ3 data with the pair (-12|12). The current result on statistics is also stored in the local file 'DATA/statseries.mat', so that any calculations can be easily performed on the histograms or time series.