CODEWITHSUNDEEP
matlabselectfilteringcontains
MichaelW112
MichaelW112

Reputation: 11

Matlab filtering records by date

I'm a little rookie in Matlab and I met some trouble with my homework

I have Excel which looks like this : 

Date          column A         column B
1/1/2015     (double)         (double)
5/1/2015     (double)         (double)
6/1/2015     (double)         (double)
12/2/2015     (double)         (double)
13/2/2015     (double)         (double)
15/3/2015     (double)         (double)
11/4/2015     (double)         (double)
12/4/2015     (double)         (double)
13/4/2015     (double)         (double)
11/5/2015     (double)         (double)
13/5/2015     (double)         (double)
11/6/2015     (double)         (double)
11/7/2015     (double)         (double)
11/8/2015     (double)         (double)
11/9/2015     (double)         (double)
11/10/2015     (double)         (double)
11/11/2015     (double)         (double)
11/12/2015     (double)         (double)
.
########(string?) ...          ...
########(string?) ...          ...
15/8/2018         ...          ...
.
.
.

I imported and converted it into a table, and now I need to filter it and leave only the first day of each quarter.

since Matlab is so different from things like MySQL, java, things I learned before and I got not much time, I'm panic in this desperate situation(it just a start of my homework!), so I really need some help.

I'm not familiar with the syntax and this the first time I asked a question, sorry if I ask something stupid.

Upvotes: 0

Views: 167

Answers (2)

MichaelW112
MichaelW112

Reputation: 11

table = readtable("a.csv");
table= table(month(table.Date)==4 | month(table.Date)==7 | month(table.Date)==10 | month(table.Date)==1, :);

just found a way that can filter specific month

now I just need to keep the first day of a month only and delete all other day

Upvotes: 1

Cibin Joseph
Cibin Joseph

Reputation: 1273

You can use the datetime class in Matlab to compare dates.

Assuming:
1. Your dates are in the format dd/MM/yyyy
2. Dates in column 1 are already sorted when printing out from Excel
3. The delimiter for the csv file titled data.csv is a space,
the following snippet should print out the columns of the first occurring date of each quarter.

clc; clear;

fid = fopen('data.csv');

% Retrieve data from file
data = textscan(fid, '%s %s %s', 'delimiter', ' ');

% Convert string to date objects 
% that enables date comparison
datesArray = datetime(data{1}, 'InputFormat', 'dd/MM/yyyy');

% Define start and end dates of each quarter
QstartDayMonth = ['01/01'; '01/04'; '01/07'; '01/10'];
QendDayMonth   = ['31/03'; '30/06'; '30/09'; '31/12'];

% Parse data to extract seasonal firsts
quart = 1;
for i = 1:length(datesArray)
  % Obtain year
  currentDate = datesArray(i);
  currentYear = num2str(currentDate.Year);

  % Define start date of current year's quarter
  quarterStart = strcat(QstartDayMonth(quart, :), '/', currentYear);
  quarterEnd   = strcat(QendDayMonth(quart, :)  , '/', currentYear);
  quarterStart = datetime(quarterStart, 'InputFormat', 'dd/MM/yyyy');
  quarterEnd   = datetime(quarterEnd, 'InputFormat', 'dd/MM/yyyy');

  % Check if current date lies in chosen quarter
  if (currentDate >= quarterStart)
    disp([data{1}{i}, '  ', data{2}{i}, '  ', data{3}{i}]);

    % If it does, advance the quarter to be checked
    quart = quart + 1;
    if (quart > 4)
      quart = 1;
    end
    continue;
  end
end
fclose(fid);

Upvotes: 0

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