如何在MATLAB中查找数组中包含特定元素的行号？

Hey there! Let's walk through how to find the row number containing [7 8] in your array a = [1 2; 3 4; 5 6; 7 8; 9 10];. There are a few straightforward, readable ways to do this in MATLAB—pick the one that fits your workflow best:

Method 1: Using ismember with Row Matching #

This is the most intuitive approach, as it directly checks for full row matches:

a = [1 2; 3 4; 5 6; 7 8; 9 10];
target = [7 8];
row_number = find(ismember(a, target, 'rows'));

• ismember(a, target, 'rows') returns a logical array where each entry is true if the corresponding row in a exactly matches target, and false otherwise.
• find() converts that logical array into the actual row index (here, it will return 4).

Method 2: Explicit Element-wise Check with all() #

If you want to break down the comparison step, use element-wise equality checks combined with all() to verify the entire row matches:

a = [1 2; 3 4; 5 6; 7 8; 9 10];
target = [7 8];
row_number = find(all(eq(a, target), 2));

• eq(a, target) compares every element in a to the corresponding element in target (MATLAB automatically broadcasts the 1x2 target to match the 5x2 size of a).
• all(..., 2) checks if all elements in each row are equal (meaning the entire row is a match).
• find() pulls out the index of the matching row.

Method 3: Sum of Absolute Differences #

Another way to confirm exact matches is to calculate the sum of absolute differences between each row and the target—if the sum is 0, the rows are identical:

a = [1 2; 3 4; 5 6; 7 8; 9 10];
target = [7 8];
row_number = find(sum(abs(a - target), 2) == 0);

• a - target subtracts the target from each row (thanks to MATLAB's broadcasting).
• abs() ensures we're only dealing with non-negative differences, and sum(..., 2) adds these values up row by row.
• Rows with a sum of 0 are perfect matches, so find() returns their indices.

Quick Note on Duplicates #

If your array has multiple rows matching target, all three methods will return all matching row indices (for example, if a had two rows of [7 8], row_number would be a vector like [4; 6]).

内容的提问来源于stack exchange，提问作者Arihant Jain