Sorting a 64 x6 table

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Yannick Tabot Njami 2019-3-13

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https://ww2.mathworks.cn/matlabcentral/answers/449851-sorting-a-64-x6-table

评论： Yannick Tabot Njami 2019-3-15

table.png

Dear All i need help with sorting a table and also new to matlab your time is appreciate

Please consider the attachment

Here is my algorithm :

ycoordinate= [20 50 80 110 140 170 200 230]

find all index example when y= 20
get the x coordinate values corresponding to to the indices y=20
get the corresponding mean_velocity,std_velocity, mean_pd ,std_pd vlalues
get them as a pair. meaning that for case when y=20 ,
x = [20 110 140 170 200 20 230 50 80] and mean_velocity=[1.3696 57.5733 57.7197 57.7133 58.0707 58.0194 58.1603 57.9150 57.7572]
then sorting them in ascending or descending order as
x=[20 20 50 80 110 140 170 200 230] mean_velocity=[1.3696 58.0194 57.9150 57.7572 57.5733 57.7197 57.7133 58.0707 58.1603 ]
and then plot mean_velocity against x. i want to do this for the the std_velocity, mean_pd ,std_pd as well.
i thought about a for loop but dont know how to go about it . please any help will be greatly appreciated
many thanks in advance

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Guillaume 2019-3-13

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For table, sortrows is probably more appropriate than sort. You can pass the variable names directly to sortrows to prioritise the sort columns:

sortrows(sometable, {'ycoordinates', 'xcoordinates'})  %to sort first by y, then x.

Guillaume 2019-3-13

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Yannick comment posted as an answer moved here (it's just code with no explanation):

Average_Table = table(xcoordinate,ycoordinate,mean_velocity,std_velocity, mean_pd ,std_pd);
for jj = 20 :30 :230
    yindex=find(ycoordinate == jj);
    %Deleting the  first index  to eliminat  the  offset value at  y=20
    if  jj ==20
        yindex(yindex==1)=[];
    end
%     getting just a table dor x  and mean_velocity 
    newX=(xcoordinate(yindex));
    newVY =mean_velocity(yindex);
    
   %generated table as a pair
    tableXY =[newX newVY]
    %     soting out the  table
preallocating memory for  sorted table
    sortedtable =zeros(length(tableXY),2)
    sortedtable(:,1)=sort(tableXY(:,1))
    sortedX = sortedtable (:,1)
%Going through each table to look for corresponding indeces and match .
    for N =1:length(tableXY)
        sortedtable(N,2:end) =tableXY(find(ismember(tableXY(:,1),sortedtable(N))),2)
        %     sorted  Y coordinates
        sortedY = sortedtable(:,2);
    end
    
    hold on 
    
 
          plot(sortedX,sortedY,'color',rand(1 ,3),'marker','*');
       xlabel('x position');
     ylabel('mean velocity');
    legend(['mean velocity against position =' num2str(jj)]);
     drawnow;
    

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Answer 1

Guillaume 2019-3-13

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If I understood correctly what you want, you basically want a plot for each unique y value which are the other variables against x. The easiest way to achieve this is:

create a function to plot the variables against x, ignoring y for now. That function therefore takes as input x, and the other variables. E.g (tailor as required):

function myplot(x, varargin)   %saved in its own m file
    %inputs:
    %    x: a possibly unsorted array of x coordinates. Will be sorted before plotting
    %    4 more inputs (for now): mean velocity, std velocity, mean pd, std pd. 
    %all inputs are column vector as they come from a table
    assert(numel(varargin) == 4, 'Only 4 variables expected');
    
    [x, order] = sort(x);
    plotvars = [varargin{:}];  %concatenate the other 4 vectors into a 4 column matrix
    plotvars = plotvars(order, :);  %and sort in the same order as x
    plot(x, plotvars);
    legend({'mean velocity', 'std velocity', 'mean pd', 'std pd'});    
end

use rowfun to call the above function for each group of unique y:

rowfun(@myplot, thetable, 'GroupingVariables', 'ycoordinates', 'InputVariables', {'xcoordinates', 'mean_velocity', 'std_velocity', 'mean_pd', 'std_pd'}); %group by y. For each group, pass x and the other columns to the function

Done!

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Guillaume 2019-3-13

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Yannick comment mistakenly posted as an answer moved here:

Here the function in its own m file :

function  myplot(x, varargin)
assert(numel(varargin)==4)
[x,order] =sorte(x);
plotvars = [varargin{:}];
plotvars =plotvars(order,:);
plot(x,plotvars);
legend({'mean velocity', 'std velocity', 'mean pd', 'std pd'})
end
%  THe replaced line  with whole of my for loop for  jj=20:30:230
 rowfun(@myplot, Average_Table, 'GroupingVariables', 'ycoordinate', 'InputVariables', {'xcoordinate', 'mean_velocity', 'std_velocity', 'mean_pd', 'std_pd'});
 here the error:
 
 Error using tabular/rowfun>dfltErrHandler (line 497)
Applying the function 'myplot' to the 1st group of rows in A generated the following error:
Too many output arguments.
.
Error in tabular/rowfun>@(s,varargin)dfltErrHandler(grouped,funName,s,varargin{:}) (line 268)
    errHandler = @(s,varargin) dfltErrHandler(grouped,funName,s,varargin{:});
Error in tabular/rowfun (line 288)
                [b_data{igrp,:}] = errHandler(struct('identifier',ME.identifier, 'message',ME.message, 'index',igrp),inArgs{:});
Error in nuzzle_20190301 (line 88)
 rowfun(@myplot, Average_Table, 'GroupingVariables', 'ycoordinate', 'InputVariables', {'xcoordinate', 'mean_velocity', 'std_velocity',
 'mean_pd', 'std_pd'}); 
>> 

Guillaume 2019-3-15

在 MATLAB Online 中打开

It probably would make sense to create a new figure for each y, and use the y to name the graph. So I'd modify the myplot function to:

function myplot(y, x, varargin)   %saved in its own m file
    %inputs:
    %    y: the y coordinate of the plot. Due to the way rowfun works this will be a column vector of identical y
    %    x: a possibly unsorted array of x coordinates. Will be sorted before plotting
    %    4 more inputs (for now): mean velocity, std velocity, mean pd, std pd. 
    %all inputs are column vector as they come from a table
    assert(numel(varargin) == 4, 'Only 4 variables expected');
    figure;
    [x, order] = sort(x);
    plotvars = [varargin{:}];  %concatenate the other 4 vectors into a 4 column matrix
    plotvars = plotvars(order, :);  %and sort in the same order as x
    plot(x, plotvars);
    legend({'mean velocity', 'std velocity', 'mean pd', 'std pd'});    
    title(sprintf('At y = %g', y(1)));
end

and the rowfun:

rowfun(@myplot, Average_Table, 'GroupingVariables', 'ycoordinate', 'InputVariables', {'ycoordinate', 'xcoordinate', 'mean_velocity', 'std_velocity', 'mean_pd', 'std_pd'}, 'NumOutputs', 0);

"but the plot produce was very strange and not what i expected"

Well without any detail of what you expected and what you got, it's difficult to give any advice.

Yannick Tabot Njami 2019-3-15

Here is what i get :

Yannick Tabot Njami 2019-3-15

here is what i expect :

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Sorting a 64 x6 table

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Sorting a 64 x6 table

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