MATLAB: How to list through words in for loop.

conditionsloop

Hello guys

I am trying to make a program that counts hours that i soend in work. I write them in following format:

sixj=[8,16.5]

Which means that on sixth of july I worked from 8 in the morning until 4:30pm. I need to count all days and apply conditions: 1. If it is after 17:00 the pay is +33% and if it is sunday, the pay is +45%. I do not want to write code for every individual day, rather i would like to use for loop to list through days and calculate it in the loop. Does anybody have any idea how I might be able to do it? Thank you very much.

Best Answer

When you put your data into one array then your calculations will be trivially easy. For example:

M = [...
    2017,07,06,08,16.5;...
    2017,07,07,09,12.0;...
    2017,07,08,10,18.7;...
    2017,07,09,07,16.2;...
    2017,07,10,07,19.9];
%  [yyyy,mm,dd,beg,end]
>> hours = diff(M(:,4:5),1,2)
hours =
        8.5
          3
        8.7
        9.2
       12.9
>> dtnum = datenum(M(:,1:3));
>> days  = weekday(dtnum);
>> issun = days==1 % detect sundays
issun =
   0
   0
   0
   1
   0
>> pay = 99;
>> hours.*~issun*pay % normal rate
ans =
      841.5
        297
      861.3
          0
     1277.1
>> hours.*issun*pay*1.45 % sunday rate
ans =
          0
          0
          0
     1320.7
          0

and we can add plots very simply too:

>> bar(vec,hours)
>> datetick('x','mmmdd')

etc, etc. Did you see what I did there? By making the data much simpler (using one numeric matrix), I made your difficult problem disappear entirely and wrote more working code is less time than it took you to write your question! How? By keeping the data together.

Related Solutions

MATLAB: How to insert a int value into the name of a variable (for loop)

Just use a non-scalar structure:

data(1).date = ...
data(2).date = ...
data(3).date = ...
data(4).date = ...

This makes it trivially easy to access the data using indexing, which is fast and efficient, e.g. the second date:

data(2).date

Not only that you can very conveniently convert any field into a comma-separated list, which makes it simple to join the field values together into one array, e.g. to put all the dates into one cell array:

out = {data.date}

or to assign them in exactly the same way.

While it is possible to define structure fieldnames dynamically, in your case (you proposed numbered field names) it serves no purpose whatsoever and will only make your code slow and complicated.

Writing neat efficient MATLAB code is easy, once you avoid bad design decisions like putting meta-data into field or variable names:

https://www.mathworks.com/matlabcentral/answers/228557-experts-of-matlab-how-did-you-learn-any-advice-for-beginner-intermediate-users

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

MATLAB: How can i save and access data in a mat file.

"i would also like your suggestions on how to name the variables..."

Don't name variables like that! Creating or accessing variable names is how beginners force themselves into writing slow, complex, buggy code that is hard toe debug. Just put the data into one array (which might be ND numeric, cell array, struct, table, etc.). Read this to know more:

https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

Don't put meta-data into variable names or fieldnames. Meta-data is data too, so store it along with your other data. If I was given your data I would store it in two arrays, the first a 3D numeric array with the measurements/sample, and the second a simple vector with the corresponding pressure values (they are numeric, so storing them as numeric will make your code simpler and more efficient). Then all you need to store is this:

A = [1000x16xN]    % 3D array of data
V = [1,10,100,...] % 1xN vector of pressure values
save(...,'A','V')

and load it

S = (...);
A = S.A;
V = S.V;

Of course you should use more descriptive names. Finding specific values in either array is trivial and efficient using indexing. How to use indexing is explained in the introductory tutorials:

https://www.mathworks.com/help/matlab/getting-started-with-matlab.html

And of course having all of the data in one array means you can trivially apply many numeric operations to it:

https://www.mathworks.com/help/matlab/matlab_prog/vectorization.html

Best Answer

Related Solutions

MATLAB: How to insert a int value into the name of a variable (for loop)

MATLAB: How can i save and access data in a mat file.

Related Question