requirement Switch & Case expression with matrix

Question

shin hsu 2019-5-29

0
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回答： shin hsu 2019-5-29

Is there a way to get aound the scalar and vector requirement for switch/ case expressions?

I have a coordinates matrix, coors = [x1 y1; x2 y2; x3 y3] and would like find out if they match a pre-defined list; for instance,

field_1 = [ x3 y3] 
field_2 = [x1 y1]
field_3 = [x2 y2]

If they match, then the 1x1 name description will be added to re-build array so that i don't distrub the orginal matrix.

it would be a cleaner syntax using "swtich' than lots of "ifs" and "elseifs"!

[r c] = size(coors);
for i = 1:r
    coor_xy = [coors(i,1) coors(i,2)];
    switch coor_xy(1)
        case coor_xy(1) == field_1(1) && coor_xy(2) == field_1(2)
            name(i) = 'field_1';
        case coor_xy(1) == field_2(1) && coor_xy(2) == field_2(2)
            name(i) = 'field_2';
       end
end

thanks guys

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Answer 1

Jos (10584) 2019-5-29

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在 MATLAB Online 中打开

I suggest you use ISMEMBER with the rows option, rather than if-else (or switch)

fieldlist = [x3 y3 ; x1 y1 ; x2 y2] ;
filedlist_names = {'field3', 'field1', 'field2'}
[tf, loc] = ismember(coor_xy, fieldlist, 'rows')
if tf
    name = fieldlist_names{loc}
else
    name = 'none'
end