How to make writetable write sub structures or tables

With the following code:

   bob = struct()
   bob.joe = 1
   bob.sam = '4'
   bob.bill = [6:10]
   bob.jim = struct('a',1,'b','q')
   writetable(struct2table(bob))

I get the following output

   joe,sam,bill_1,bill_2,bill_3,bill_4,bill_5,jim
   1,4,6,7,8,9,10,

So the structure entry for 'jim' is just blank.

If I turn jim into a table

   bob.jim = struct2table(bob.jim)
   writetable(struct2table(bob))

The output now has the _1 and _2 for jim, but they are blank

   joe,sam,bill_1,bill_2,bill_3,bill_4,bill_5,jim_1,jim_2
   1,4,6,7,8,9,10,,

So how do I get writetable to deal with this? Preferably I would want the header to come out

   joe,sam,bill_1,bill_2,bill_3,bill_4,bill_5,jim.a,jim.b
   1  ,4  ,6     ,7     , 8    ,9     ,10    ,1    ,q

Also, if I am not writing to a spreadsheet, I would liek the ability to not expand arrays, so it would look like

   joe,sam,    bill,     jim.a,jim.b
   1  ,4  ,[6,7,8,9,10] ,1    ,q

Answer 1

[Himanshu]

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