Append a file, Error using save, File may be corrupt

I am attempting to append either a cell or structure to a file, I have tried both, to either an .xlsx or .mat file, I have tried both.

data = uigetfile('*.mat');
s = load(data);
date = regexp(data, '\d+_\d+', 'match');
file = (s.details);

% Comment on data
comment = 'NaN';

% Create cell
IAMHS_f = [date comment file(1,1) file(1,2) file(1,3) file(1,4)];

% Create stucture
% headings = {'Date' 'Comments' 'Mean' 'Min' 'Max' 'Std'};
% IAMHS_f2 = cell2struct(IAMHS_f,headings, 2)

%%Save and append parameter
savdir = 'C:\Users\Tim\Documents\AI-LLC\DATA\2ndary\DailyDetails\FinalPlots'
save(fullfile(savdir,'IAMHS.mat'),'IAMHS_f','-append')

The files I have tried appending are empty .mat and .xlsx files. When I do so I get (Error using save, File may be corrupt)

I have also tried saving one set of data first and then doing an append feature and it appears like it overwrites the existing data. I would prefer to be able to save the first set of data without having to make any adjustments to my code to append it.

I essentially have a 1x6 (cell or structure) and want to save it and continue adding rows.

Answer 1

[dpb]

As the English definition implies, "append" means there's got to be something already there to append to. While computer-language definitions don't always have a direct correlation to the equivalent word in common usage, it appears that is the case with save.

>> dir x.*
'x.*' not found.
>> save x -append
Error using save
Unable to write file x: No such file or directory. 
>>

It errors if there isn't an existing .mat file on which to append the existing array.

>> save x
>> save x -append
>> delete x.mat
>> x=[];
>> save x
>> x=rand(10,1);
>> save x -append
>> clear x
>> load x
>> whos x
Name       Size            Bytes  Class     Attributes
x         10x1                80  double              
>>

Closest I could come was to create an empty file first; you could do that as part of an initialization step and then the remaining code could, it appears, be identical even for the first "real" case.