4.4: Extracting Rows, Columns, and Subarrays

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Page ID: 136622

Zara Noroozi
Irvine Valley College

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Once a matrix is created, we often do not want the entire matrix. We might want one row, one column, or a smaller section. MATLAB makes this easy with indexing and the colon operator.

Example \(\PageIndex{1}\)

Extracting a block of data.

mat2 = [2 10 5; 6 20 17; 13 2 0];

data_1 = mat2(1,:)      % entire first row

data_2= mat2(:,3)      % entire third column

data_3 = mat2([2,3],[1,2])  % rows 2 and 3, columns 1 and 2

Solution

The colon symbol means "all" in this context. So mat2(1,:) means row 1 and all columns. Similarly, mat2(:,3) means all rows and column 3.

data_1 =

    2   10    5

data_2 =

    5
   17
    0

data_3 =

    6   20
   13    2

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