How to dynamically change name of table?

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Marina
Marina 2024-4-10
评论： Voss 2024-4-11
This code below is just a very simple example of some analysis I am doing with my experimental results.
I am running 5 cycles of an experiment, results come out in a long txt file, I want to plot everything with a different color based on cycle number. So I am creating sub-tables from the main table based on the parameter of interest. This simple code works parfectly. However, it's fine because it is only 5 runs. What if it was 100?
Is there a more efficient way to assign table names dynamically? I am new with Matlab and I am using my real life needs to practice and learn.
Thank you!
T=readtable("Output-C1_Cu.txt","NumHeaderLines",2);
NT1=T(T.Var2==1,:);
NT2=T(T.Var2==2,:);
NT3=T(T.Var2==3,:);
NT4=T(T.Var2==4,:);
NT5=T(T.Var2==5,:);
plot(NT1,"Var4","Var6",LineWidth=1.5, Color=[0 0.4470 0.7410])
hold on
plot(NT2,"Var4","Var6",LineWidth=1.5, Color=[0.8500 0.3250 0.0980])
hold on
plot(NT3,"Var4","Var6",LineWidth=1.5, Color=[0.9290 0.6940 0.1250])
hold on
plot(NT4,"Var4","Var6",LineWidth=1.5, Color=[0.4940 0.1840 0.5560])
hold on
plot(NT5,"Var4","Var6",LineWidth=1.5, Color=[0.4660 0.6740 0.1880])
hold off
xlim([0,1.5])
xlabel('V cell (V)','FontWeight','bold')
ylabel("dQ/dV cell (mAh/V)","FontWeight","bold")
title('Treated Cu - OG Si')
legend({'Cycle 1','Cycle 2','Cycle 3','Cycle 4','Cycle 5',}, ...
'Location','southeast')
  2 个评论
Stephen23
Stephen23 2024-4-10
编辑：Stephen23 2024-4-10
"Is there a more efficient way to assign table names dynamically? "
No, there is not. Every way is slow, inefficient, complex, and pointlessly obfuscates code:
https://www.mathworks.com/matlabcentral/discussions/tips/849901-tutorial-why-variables-should-not-be-named-dynamically-eval
MATLAB is designed around arrays and indexing. Indexing is exactly how you would handle "What if it was 100?", because indexing trivially expands to any size (hint: try using a loop). Indexing is exactly how experienced MATLAB users would do it, or by using the inbuilt tools for processing groups of data:
https://www.mathworks.com/help/matlab/matlab_prog/perform-calculations-by-group-in-table.html
https://www.mathworks.com/help/matlab/matlab_prog/grouped-calculations-in-tables-and-timetables.html
Your approach of copy-pasting lots of code or dynamically naming variables ... is best avoided.
"I am new with Matlab and I am using my real life needs to practice and learn."
Then forget about dynamic variable names. That is a path you really don't want to go down:
https://www.mathworks.com/matlabcentral/discussions/tips/847916-experts-of-matlab-how-did-you-learn-any-advice-for-beginner-intermediate-users/2556966#reply_2556966

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采纳的回答

Voss
Voss 2024-4-10
Ran in:
One way to plot the table data for each cycle separately, without having to create a new table variable for each cycle, is to use findgroups and splitapply.
% make up a table
Var = randi([1,10],40,6);
Var(:,4) = Var(:,4)/10;
T = array2table(Var)
T = 40x6 table
Var1 Var2 Var3 Var4 Var5 Var6 ____ ____ ____ ____ ____ ____ 7 10 3 0.1 6 9 2 5 9 0.4 8 1 9 8 8 0.6 8 8 8 9 6 0.6 9 7 7 3 1 0.4 2 8 5 8 7 0.5 4 2 8 9 7 1 3 5 1 9 9 0.9 5 2 7 4 8 0.6 4 2 7 4 2 0.9 1 6 10 9 6 0.2 5 5 8 1 2 0.9 9 2 8 2 9 0.6 6 8 10 6 7 0.9 1 1 10 7 2 0.9 3 4 5 5 6 0.3 10 10
% plot Var6 vs Var4 separately for each Var2 group
figure
hold on
[G,GID] = findgroups(T.Var2);
F = @(varargin)plot(varargin{4},varargin{6},LineWidth=1.5);
splitapply(F,T,G)
hold off
xlim([0,1.5])
xlabel('V cell (V)','FontWeight','bold')
ylabel("dQ/dV cell (mAh/V)","FontWeight","bold")
title('Treated Cu - OG Si')
legend("Cycle "+GID,'Location','southeast')
Also running your code to plot the first 5 groups, for comparison/validation:
NT1=T(T.Var2==1,:);
NT2=T(T.Var2==2,:);
NT3=T(T.Var2==3,:);
NT4=T(T.Var2==4,:);
NT5=T(T.Var2==5,:);
figure
hold on
plot(NT1,"Var4","Var6",LineWidth=1.5, Color=[0 0.4470 0.7410])
plot(NT2,"Var4","Var6",LineWidth=1.5, Color=[0.8500 0.3250 0.0980])
plot(NT3,"Var4","Var6",LineWidth=1.5, Color=[0.9290 0.6940 0.1250])
plot(NT4,"Var4","Var6",LineWidth=1.5, Color=[0.4940 0.1840 0.5560])
plot(NT5,"Var4","Var6",LineWidth=1.5, Color=[0.4660 0.6740 0.1880])
hold off
xlim([0,1.5])
xlabel('V cell (V)','FontWeight','bold')
ylabel("dQ/dV cell (mAh/V)","FontWeight","bold")
title('Treated Cu - OG Si')
legend({'Cycle 1','Cycle 2','Cycle 3','Cycle 4','Cycle 5',}, ...
'Location','southeast')
  9 个评论
显示 7更早的评论
Voss
Voss 2024-4-11
Ran in:
By the way, it may be convenient to collect each groups' data together, into say a cell array of tables, rather than just plotting it directly. Then you can plot it afterward or do whatever else you need to do on a group-by-group basis. Here's one way of doing that:
% make up a table
Var = randi([1,10],40,6);
Var(:,4) = Var(:,4)/10;
T = array2table(Var)
T = 40x6 table
Var1 Var2 Var3 Var4 Var5 Var6 ____ ____ ____ ____ ____ ____ 8 8 4 1 10 5 8 5 10 0.2 5 6 8 3 6 0.8 7 6 7 7 3 0.3 10 3 10 9 6 0.9 10 1 2 9 8 0.5 6 7 2 10 2 0.1 4 6 5 7 3 0.9 7 3 4 8 4 0.7 8 4 7 6 5 0.1 10 5 7 6 7 0.3 7 10 8 5 1 0.6 6 10 6 6 7 0.5 4 5 4 4 1 0.1 8 2 8 1 5 0.7 5 3 7 6 1 0.8 9 8
% collect groups of data
[G,GID] = findgroups(T.Var2);
F = @(varargin){table(varargin{:})};
C = splitapply(F,T,G)
C = 10x1 cell array
{4x6 table} {3x6 table} {6x6 table} {2x6 table} {6x6 table} {6x6 table} {3x6 table} {4x6 table} {4x6 table} {2x6 table}
C{1} % group 1 data
ans = 4x6 table
Var1 Var2 Var3 Var4 Var5 Var6 ____ ____ ____ ____ ____ ____ 8 1 5 0.7 5 3 2 1 2 0.6 8 7 2 1 10 0.8 9 7 10 1 6 0.3 4 7
% plot Var6 vs Var4 separately for each Var2 group
figure
hold on
for ii = 1:numel(C)
plot(C{ii}.Var4,C{ii}.Var6,LineWidth=1.5)
end
hold off
xlim([0,1.5])
xlabel('V cell (V)','FontWeight','bold')
ylabel("dQ/dV cell (mAh/V)","FontWeight","bold")
title('Treated Cu - OG Si')
legend("Cycle "+GID,'Location','southeast')
Here the anonymous function F
F = @(varargin){table(varargin{:})};
makes a cell array containing one table of data. Then (as before) splitapply runs that function for each group, so you get C, a cell array containing a table of data for each group.

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