at its midpoint 130 lines 126 and 128 thereby define an arc 132 any polygonal lines e g 134 136 between parallel coordinate axes 50 and 52 whose slopes lie within arc 132 are thereby selected and are either highlighted or otherwise emphasized on the display the corresponding cartesian coordinate presentation of the flow query is shown in fig1 lines 120 39 and 124 39 are the lines that are defined by the parallel coordinates at the tips of arrows 120 and 124 respectively along parallel coordinate axis 52 because arrows 120 and 124 lie on parallel coordinate axis 52 it is known that their corresponding lines 120 39 124 39 will be at an angle of 45 u00b0 with respect to the origin in the cartesian coordinate system because polygonal lines 134 and 136 in fig1 evidence slopes within arc 132 their respective data points in fig1 134 39 136 39 fall between half spaces defined by lines 120 39 and 124 39 the flow query enables a user to identify independent variables which exhibit a similar slope in the parallel coordinate system between adjacent dependent variables the mathematical representation of the flow query is as follows it may occur in the parallel coordinate display that no data value is specified for one or more parallel coordinate axes in such case the parallel coordinate procedure in memory 30 fig6 includes a default condition wherein a default data value is entered for such missing value the default data value is calculated as 5 less than the minimum value plotted on corresponding the parallel coordinate axis thus when a polygonal line is shown on the parallel coordinate presentation the polygonal line extends below the.