Create table from array in a loop

Hi all,

I am working on code that is able to read two columns of data (Diameter and height ) belonging to various Excel spreadsheets pertaining to collected data so that these can be grouped in 5mm groups according to a Diameter values.

My first approach was to produce a specific code for each project as described below, so that in the end I could work from the data populated as per table Vtotal:

rawTable = readtable('20220209_Diameter.xlsx','Sheet','ExportResult');

x = rawTable.x; %: Column x

y = rawTable.y; %: Column y

V835 = rawTable((rawTable.x > 830) & (rawTable.x <= 835),:);

V835M = table2array(V835(:,2:3));

V835M(:,3)=835;

V835N = array2table(V835M,'VariableNames',{'x','y','z'});

V840 = rawTable((rawTable.x > 835) & (rawTable.x <= 840),:);

V840M = table2array(V840(:,2:3));

V840M(:,3)=840;

V840N = array2table(V840M,'VariableNames',{'x','y','z'});

Vtotal = [V835N; V840N; V845N; V850N; V855N; V860N; V865N; V870N; V875N; V880N];

Xtotal = Vtotal.z;

Ytotal = Vtotal.y;

boxplot(Ytotal, Xtotal)

I would now be looking to create a standard code that is able to read any set of data belonging to the different spreadsheets mentioned above, so have produced the following code.

range=5;

rawTable = readtable('20220209_Diameter.xlsx','Sheet','ExportResult');

x = rawTable.x; %: Column x

y = rawTable.y; %: Column y

Diam_min=790; % Add minimum diameter

Diam_max=860; % Add maximum diameter

n_div=(Diam_max-Diam_min)/range;

Diam=x;

Sh=y;

for j=1:n_div

V = rawTable((rawTable.x > (Diam_min+(j-1)*range)) & (rawTable.x <= (Diam_min+j*range)),:);

VM = table2array(V(:,2:3));

VM(:,3)=Diam_min+j*range-range/2; % Valor en el que centramos el boxplot en "X"

VN = array2table(VM,'VariableNames',{'x','y','z'});

end

What I require, is the above Vtotal table to be populated after each iteration so that I get the same sort of data as above and bearing in mind that the data amount and grouping will vary between spreadsheets.

Answer 1

[Stephen23]

"to collected data so that these can be grouped in 5mm groups according to a Diameter values."

The MATLAB approach would be to use some simple, very efficient mathematics. For example:

X = 800+23*rand(9,1);
Y = 32*rand(9,1);
T = table(X,Y) % your input data

T = 9×2 table
      X         Y   
    ______    ______

    821.92    10.806
    807.72    6.1337
    820.14    2.1696
    817.15    3.2259
    804.68    9.4653
    820.68      12.7
    801.18    9.8082
       813    1.2345
    809.27    18.478

T.G = 5*ceil(T.X/5)

T = 9×3 table
      X         Y        G 
    ______    ______    ___

    821.92    10.806    825
    807.72    6.1337    810
    820.14    2.1696    825
    817.15    3.2259    820
    804.68    9.4653    805
    820.68      12.7    825
    801.18    9.8082    805
       813    1.2345    815
    809.27    18.478    810

boxplot(T.Y,T.G)

Vtotal = sortrows(T,'G')

Vtotal = 9×3 table
      X         Y        G 
    ______    ______    ___

    804.68    9.4653    805
    801.18    9.8082    805
    807.72    6.1337    810
    809.27    18.478    810
       813    1.2345    815
    817.15    3.2259    820
    821.92    10.806    825
    820.14    2.1696    825
    820.68      12.7    825

[Stephen23]

"What I would be looking is the Vtotal table .."

You can simply SORTROWS the table by the grouping variable. I added that to my answer.

[CB]

Hi Stephen,

Thank you so much.

kind regards,

Cesar

[Stephen23]

@CB: another option would be to use DISCRETIZE:

https://www.mathworks.com/help/matlab/ref/double.discretize.html

which would allow you to define the bin edges as a simple numeric vector.

Answer 2

[Peter Perkins]

In addition to what Stephen has said, this code (which as Stephen points out was unncessary)

V835 = rawTable((rawTable.x > 830) & (rawTable.x <= 835),:);
V835M = table2array(V835(:,2:3)); 
V835M(:,3)=835;
V835N = array2table(V835M,'VariableNames',{'x','y','z'});

could have been much simpler. I would think something like this:

V835N = rawTable((rawTable.x > 830) & (rawTable.x <= 835),["x" "y"]);
V835.z(:) = 835;

People tend to overuse table2array/array2table. Often just a dot works.