Function [cm,icmsecond] = bluered(n,icmsecond,reverse,compress,show) returns colourmap cm (matrix of three columns for the red-green-blue colour values from 0 to 1, inclusively) with n colours, which form two parts: the first part ranges from blue to cyan and the second part from yellow to red. If input argument n is not given at input, it defaults to 20. Input argument icmsecond holds the row index in the colourmap where the second part ranging from yellow to red starts. If the argument is not given at input, it is calculated by: icmsecond = floor(n/2) + 1; and thus both parts have approximately the same number of colours. The eventual value of icmsecond is also available in the second output argument. If input argument reverse is true, the colours range from cyan to blue and from red to yellow. If the argument is not given at input, it defaults to false. If input argument compress is true, the colours of the first part, i.e. with indices < icmsecond, range fully between the extreme blue and cyan tones, and the second part, i.e. with indices >= icmsecond, range fully between the extreme yellow and red tones. If input argument compress is false, the colours of each part have an equal gradation (the tones vary with the same "steepness"). If the argument is not given at input, it defaults to false. If input argument show is true, the colourmap is plotted in two figures on screen. If the argument is not given at input, it defaults to false. (c) 2026 fabien van mook 2026.08.20 release of this file within package "fvm-colourgrade" under GNU GPLv3+