MATLAB: Does setdiff answer depend on order of arguments

cell stringssetdiff

>>bob = {'a','b','c'};
>>bill = {'a','b','c', 'd','e'}

As expected,

>>A = setdiff(bill,bob)
A = 
    'd'    'e'

BUT

>> B = setdiff(bob,bill)
B = 
   Empty cell array: 1-by-0

WHY??

Best Answer

Were you expecting the output to contain elements that are only in one of the inputs but not both? That's not what setdiff does. If that is what you want to do, use setxor instead.

Related Solutions

MATLAB: Comparing categorical arrays in terms of content

ismember alone can answer the first point (common elements of A and B) but not the 2nd since it only tests whether elements of A are in B but not whether elements of B are in A. For example,

A = categorical({'a' 'b' 'c' 'e'}');
B = categorical({'a' 'b' 'c' 'd'}');
[LIA,LOCB] = ismember(A,B)
LIA = 4x1 logical array
   1
   1
   1
   0
LOCB = 4×1
     1
     2
     3
     0

setxor can show their differences.

[C,~,~] = setxor(A,B)
C = 2×1 categorical array
     e 
     d

MATLAB: How to make writetable write sub structures or tables

Hello Scott

As of MATLAB R2018b, "writetable" is not supported for nested tables. However, you can achieve something similar using the following workaround:

1. Create a file transformStruct.m with following contents

% Function to transform column with structure entries.
% It takes in a structure array and return two column 
% arrays, one for each field of the structure
function [a b] = transformStruct(stArr)
a=[];
b={};
for i=1:length(stArr)
    a(i) = stArr(i).a;
    b{i} = stArr(i).b;
end
a=a';
b=b';
end

2. A file transformArr.m with following contents

% Function to transform column with array entries.
% It takes in a double array and returns a cell array of strings
function out = transformArr(arr)
out = {};
for i=1:size(arr,1)
    out{i} = mat2str(arr(i,:));
end
out=out';
end

3. Finally a file main_script.m with contents

% create structure data with 3 rows
bob = struct();
bob.joe = [1; 2; 3];
bob.sam = ['4'; '5'; '6'];
bob.bill = [[6:10]; [11:15]; [16:20]];
bob.jim = [struct('a',1,'b','q'); struct('a',2,'b','r'); struct('a',3,'b','s')];
% create table from structure data
joe = bob.joe;
sam = bob.sam;
% transform the column bill to a cell array, so it 
% does not split into separate columns
bill = transformArr(bob.bill);
% transform the column jim into two separate columns, one
% for each field 
[jim_a jim_b] = transformStruct(bob.jim);
T = table(joe, sam, bill, jim_a, jim_b);
% write table to file
writetable(T)

Place all three files in a directory, and run the file main_script.m

Best Answer

Related Solutions

MATLAB: Comparing categorical arrays in terms of content

MATLAB: How to make writetable write sub structures or tables

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