Find function misbehaves when Indexing into array

I have a function which searches an array for the first value which is below a given tolerance. First, it creates a logic array using the input and a "less than" condition. Then it finds the index of the first instance of "True" in the LogicArray using the find function. If no "True" value could be found, it sets the index to be the last value in the array (in this case, 125). Then it uses the found index value to return a corresponding array value.    function [FindIndex, RxComplete] = IndexCheck(x,y) Tolerance = 100; LogicArray = x < Tolerance; FindIndex = find(LogicArray,1,'first'); if isempty(FindIndex) FindIndex = 125; end RxComplete = y(FindIndex,1); end The function is then applied to a cell array using cellfun. [Index_output, Array_output] = cellfun(@IndexCheck, x, y, 'UniformOutput',false); The code works for the above application, but it mesbehaves when I try to only search certain elements of my input array. For example, I want the function to skip the first 5 elements of the array so I index into LogicArray with (5:end). This should tell the find function to only start searching for a "True" after the first 5 elements. function [FindIndex, RxComplete] = IndexCheck(x,y) Tolerance = 100; LogicArray = x < Tolerance; FindIndex = find(LogicArray(5:end),1,'first'); if isempty(FindIndex) FindIndex = 125; end RxComplete = y(FindIndex,1); end But when I include this indexing condition for FindIndex, the function no long works and returns index and array values that do not satisfy the Tolerance condition. (i.e index values which correspond to an array value that is greater than 100).   I can trim the data to remove the first five elements, but this feels like a bandaid solution which doesn't address the issue. I'm hoping someone can help me understand why this is happening.