Find max within due date and find max within due date by class section
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I am able to find the max of the date_submitted. How do I find the max of the date_submitted but within the Lab_due_date column? Also, how do I find the max of the date_submitted within the Lab_due_date by class_section?
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Accepted Answer
Ayush Modi
on 20 May 2024
Edited: Ayush Modi
on 20 May 2024
Hi,
To find the latest date_submitted that is before the Lab_due_date for each class_section, you first need to format the data in the two column to be comparable. You can acheive this using datatime function.
data.date_submitted = datetime(data.date_submitted, 'InputFormat', 'MM/dd/yyyy HH:mm');
data.Lab_due_date = datetime(data.Lab_due_date, 'InputFormat', 'MM/dd/yyyy, hh:mm a zzz', 'TimeZone', 'America/Chicago', 'Locale', 'en_US');
data.Lab_due_date.TimeZone = '';% Group by user_id
Then, group the data by the desired category using findgroups function.
grouped = findgroups(data.user_id);
To get the date_submitted that is before the Lab_due_date:
uniqueGroups = unique(data.class_section); % Assuming class_section is a cell array of strings
maxDatesByGroup = NaT(size(uniqueGroups)); % Preallocate with Not-a-Time (NaT)
for i = 1:length(uniqueGroups)
% Filter data for the current group using strcmp for cell array comparison
currentGroupFilter = strcmp(data.class_section, uniqueGroups{i});
currentGroupData = data(currentGroupFilter, :);
% Ensure Lab_due_date and date_submitted are datetime arrays before comparison
validSubmissions = currentGroupData.date_submitted <= currentGroupData.Lab_due_date(1);
% Find the maximum date_submitted that meets the criteria
if any(validSubmissions)
maxDatesByGroup(i) = max(currentGroupData.date_submitted(validSubmissions));
end
end
Please refer to the following MathWorks documentation for more information on:
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More Answers (1)
Peter Perkins
on 29 May 2024
This is much simpler than the accepted answers suggests. And you want to use categorical for categorical data, not text.
%t = readtable("lab3_14_37_lower_participants_copy.csv");
%t.date_submitted.TimeZone = "America/Chicago";
%t.Lab_due_date = datetime(t.Lab_due_date,InputFormat="MM/dd/uuuu, HH:mm a z",TimeZone="America/Chicago")
I'm gonna assume you don't want to work with time zones; your updated file does not contain the CDT offsets.
t = readtable("https://www.mathworks.com/matlabcentral/answers/uploaded_files/1702791/lab3_14_37_lower_participants_copy_update.csv");
t = convertvars(t,["user_id" "email" "class_section"],"categorical");
Your file has exactly one unique due date. Let's add some more data.
n = 50;
t = [t; t; t]
t.date_submitted(51:100) = t.date_submitted(51:100) + calmonths(1);
t.Lab_due_date(51:100) = t.Lab_due_date(51:100) + calmonths(1);
t.date_submitted(101:150) = t.date_submitted(101:150) + calmonths(2);
t.Lab_due_date(101:150) = t.Lab_due_date(101:150) + calmonths(2);
Now that that's done, computing the max submit dates is one line. No loops.
groupsummary(t,"Lab_due_date","day","max","date_submitted")
With two grouping vars, still one line.
groupsummary(t,["Lab_due_date" "class_section"],["day" 'none'],"max","date_submitted")
2 Comments
Peter Perkins
on 29 May 2024
doc groupsummary: "You also can specify method as a function handle that returns one output per group whose first dimension has length 1. For table input data, the function operates on each table variable separately."
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