requirement Switch & Case expression with matrix

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shin hsu
shin hsu on 29 May 2019
Answered: shin hsu on 29 May 2019
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

Answers (2)

Jos (10584)
Jos (10584) on 29 May 2019
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

shin hsu
shin hsu on 29 May 2019
thanks a lot, 'ismember' cover more incidents than i need for sure.

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