Saving values from a for loop in a table

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Hey! I am trying to use a loop within a loop to extract maximum temperature for a specified cycle and index. So basically I first try to find rows for a given index and then use the second for loop to find maximum temperature in a specified cycle within that index. However, MATLAB seems to overwrite the values and only stored the last iteration in my table. What am I doing wrong?
Code:
temp = [1;2;4;5;1;8;3;4]; % temperature
ind = [1;1;1;1;2;2;2;2]; % index
cycle = [1;1;2;2;1;1;2;2]; % cycle
f = table(cycle,temp,ind);
in = unique(ind);
inx = unique(cycle);
tab = table;
for i = 1:length(in)
rows = find( ind == in(i))
for j = 1:length(inx)
tab.tmax(j) = max(f.temp(j))
end
end

Accepted Answer

Steven Lord
Steven Lord on 5 Jan 2022
temp = [1;2;4;5;1;8;3;4]; % temperature
ind = [1;1;1;1;2;2;2;2]; % index
cycle = [1;1;2;2;1;1;2;2]; % cycle
f = table(cycle,temp,ind)
f = 8×3 table
cycle temp ind _____ ____ ___ 1 1 1 1 2 1 2 4 1 2 5 1 1 1 2 1 8 2 2 3 2 2 4 2
I'm not entirely sure your nested loops do what you want, but I think what you want is something like this:
tab2 = groupsummary(f, ["ind", "cycle"], 'max', 'temp')
tab2 = 4×4 table
ind cycle GroupCount max_temp ___ _____ __________ ________ 1 1 2 2 1 2 2 5 2 1 2 8 2 2 2 4
Use the ind and cycle variables in your table f as the grouping variables and operate on the data variable temp, computing the summary statistic max. Looking at row 3 of tab2, the values of temp for ind == 2 and cycle == 1 in f are 1 and 8 and indeed the maximum of those two values is the 8 in row 3 of the variable max_temp in tab2.

More Answers (1)

Rik
Rik on 5 Jan 2022
Your index only depends on j, so it will overwrite all previous results.
Why don't you use a rectangular array to hold the maximum temperature?
temp = [1;2;4;5;1;8;3;4]; % temperature
ind = [1;1;1;1;2;2;2;3]; % index
cycle = [1;1;2;2;1;1;2;2]; % cycle
accumarray([ind cycle],temp,[],@max,NaN)
ans = 3×2
2 5 8 3 NaN 4
(I changed the last element of ind to show you the rows and columns)
  1 Comment
Liliya Vasilevich
Liliya Vasilevich on 5 Jan 2022
this seems like a clever solution! But is there a way to get it working with the loop? Since I want to store the values in a table

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