How can I discard some unwanted rows from a matrix in Matlab? -

i have matrix

a= [1 2 3 4; 5 6 7 8; 9 10 11 12; 13 14 15 16; 17 18 19 20]

i want calculation on matrix. not need rows. have discard of rows above matrix before doing calculation. after discarding 3 rows, have new matrix.

b= [1 2 3 4; 9 10 11 12; 17 18 19 20];

now have use b make other calculations. how can discard of unwanted rows matrix in matlab? suggestion helpful. thanks.

try this: (use when no. of rows keep lesser)

%// input a = [1 2 3 4; 5 6 7 8; 9 10 11 12; 13 14 15 16; 17 18 19 20];  %// rows (1-3,5) wanted keep b = a([1:3, 5],:)

output:

b =   1     2     3     4  5     6     7     8  9    10    11    12 17    18    19    20

alternative: (use when no. of rows discard lesser)

%// rows 2 , 3 discarded a([2,3],:) = [];

output:

>>  =   1     2     3     4 13    14    15    16 17    18    19    20

note: here (in alternate method), output replaces original a. need a if need afterwards. before discarding operation backup input matrix

%// input backed in b b = a;

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