Saving values from a for loop in a table

Question

Liliya Vasilevich 2022-1-5

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1622765-saving-values-from-a-for-loop-in-a-table

评论： Liliya Vasilevich 2022-1-5

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

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Steven Lord 2022-1-5

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1622765-saving-values-from-a-for-loop-in-a-table#answer_868555

在 MATLAB Online 中打开

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.

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Liliya Vasilevich 2022-1-5

thank you!! :)

请先登录，再进行评论。

Answer 2

Rik 2022-1-5

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1622765-saving-values-from-a-for-loop-in-a-table#answer_868550

在 MATLAB Online 中打开

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