How do I sum the values of sections of a table?

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Macy
Macy 2023-2-8
回答： Tushar Behera 2023-2-8
Ran in:
Hi there. I have this data, for which I created a new vector called schoolyear. How do I sum the total number of students for each schoolyear and save each value into a new vector or matrix?
So for example, the new vector totalstudents should read: 50, 66.
One suggestion I have been given is to use a for loop with possibly an if/then.
Note this is a sample of a much larger data set.
Thank you.
clc;
close all;
clear all;
table_a = readtable('Data1.xlsx');
%Create the new vector, schoolyear
for i = 1:height(table_a)
if table_a.month(i)>=8
schoolyear(i) = table_a.year(i) + 1;
else
schoolyear(i) = table_a.year(i);
end
end
table_a.schoolyear = schoolyear(:)
table_a = 9×5 table
month day year students schoolyear _____ ___ ____ ________ __________ 8 7 2000 12 2001 9 8 2000 14 2001 9 9 2000 13 2001 3 11 2001 11 2001 8 3 2001 17 2002 12 15 2001 14 2002 2 2 2002 10 2002 5 1 2002 9 2002 7 3 2002 16 2002

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采纳的回答

Tushar Behera
Tushar Behera 2023-2-8
Hi Macy,
I believe you want to group the students by the year and find the total.
This can be acheived by using the function "splitapply". This function apply a function to a group of data. For example:
clc;
close all;
clear all;
table_a = readtable('Data1.xlsx');
%Create the new vector, schoolyear
for i = 1:height(table_a)
if table_a.month(i)>=8
schoolyear(i) = table_a.year(i) + 1;
else
schoolyear(i) = table_a.year(i);
end
end
table_a.schoolyear = schoolyear(:)
g=findgroups(table_a.schoolyear)%find the groups in the data
grouped_students_total= splitapply(@sum, table_a.students, g);%get the sum from the groups
Here in "grouped_students_total" you will find your desired result. To know more about "splitapply" you can follow the following documentation:
Split data into groups and apply function - MATLAB splitapply (mathworks.com)
I hope this resolves your query.
Regards,
Tushar

更多回答（1 个）

Voss
Voss 2023-2-8
Ran in:
table_a = readtable('Data1.xlsx');
%Create the new vector, schoolyear
for i = 1:height(table_a)
if table_a.month(i)>=8
schoolyear(i) = table_a.year(i) + 1;
else
schoolyear(i) = table_a.year(i);
end
end
table_a.schoolyear = schoolyear(:);
Here's one way:
table_summary = groupsummary(table_a,'schoolyear',@sum,'students')
table_summary = 2×3 table
schoolyear GroupCount fun1_students __________ __________ _____________ 2001 4 50 2002 5 66

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