I need a little help with tables.

The task wants a table in return, where:

-the first column shows the time,

-the second column shows numbers (from -5 to 5),

-the third column shows the grades (they are strings) determined by rounding the numbers in the second column

-and the columns are named: ido, eredmeny and ertekeles.

This is the code Ive found on one of the older sites with the same task, but it doesnt work.

function tbl = f91()
t = 0:0.001:pi;

for i=1:length(t)
    switch round(abs(5*sin(3*exp(t(i)))))
        case 1
            et{i, 1} = 'elegtelen'
        case 2
            et{i, 1} = 'elegséges'
        case 3
            et{i, 1} = 'kozepes'
        case 4
            et{i, 1} = 'jo'
        case 5
            et{i, 1} = 'jeles'
        otherwise
            et{i, 1} = 'elegtelen'
    end     
end     

tbl = table(t', 5*sin(3*exp(t')), et, 'VariableNames', {'ido', 'eredmeny', 'ertekeles'});

end

[Chuguang Pan]

It can work.

[Dyuman Joshi]

It is working.

If the output is not what it is expected to be, mentioned that explicitly.

Use round while defining your table, round(5*sin(3*exp(t')))

t = 0:0.001:pi;
for i=1:length(t)
    switch round(abs(5*sin(3*exp(t(i)))))
        case 1
            et{i, 1} = 'elegtelen';
        case 2
            et{i, 1} = 'elegséges';
        case 3
            et{i, 1} = 'kozepes';
        case 4
            et{i, 1} = 'jo';
        case 5
            et{i, 1} = 'jeles';
        otherwise
            et{i, 1} = 'elegtelen';
    end     
end     
tbl = table(t', 5*sin(3*exp(t')), et, 'VariableNames', {'ido', 'eredmeny', 'ertekeles'})

tbl = 3142×3 table
     ido     eredmeny      ertekeles  
    _____    ________    _____________

        0     0.7056     {'elegtelen'}
    0.001    0.69074     {'elegtelen'}
    0.002    0.67586     {'elegtelen'}
    0.003    0.66096     {'elegtelen'}
    0.004    0.64603     {'elegtelen'}
    0.005    0.63109     {'elegtelen'}
    0.006    0.61612     {'elegtelen'}
    0.007    0.60114     {'elegtelen'}
    0.008    0.58613     {'elegtelen'}
    0.009     0.5711     {'elegtelen'}
     0.01    0.55606     {'elegtelen'}
    0.011    0.54099     {'elegtelen'}
    0.012     0.5259     {'elegtelen'}
    0.013     0.5108     {'elegtelen'}
    0.014    0.49567     {'elegtelen'}
    0.015    0.48052     {'elegtelen'}

Answer 1

[Sayan]

Hi Tamás Zsombor Tolvaj,

I understand from your issue that column 2 of your table with the name "eredmeny" should be within the desired value, i.e., -5 to 5 in the table.It is showing the same in your code too.

However, you can follow the below code snippet as an alternative to find the same.

%you can randomly generate the uniformly distributed values
%for t in the range of (-pi/2 to pi/2)
t=-pi/2+rand(1,N)*pi %Here N data points are taken,you can change the value as per requirement
%run the other part of the code as mentioned in the question
%Change the values of second column using this new equation to find the
%range of -5 to 5
tbl.eredmeny=(5*sin(t))';

You can further find more information on "table" and "rand" function in the following MATLAB documentation

• "table": https://www.mathworks.com/help/matlab/ref/table.html
• "rand":https://www.mathworks.com/help/matlab/ref/rand.html

Hope this helps you in resolving the issue.

Answer 2

[Image Analyst]

Like some of the others said, the code is working in that it does give numbers in column 2 in between -5 and 5 (if that's what you meant by "not working"). However it can be improved in several ways, and I do that here:

% Initialization steps.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;

tic
tbl = f91();
toc

Elapsed time is 0.035508 seconds.

% Find range of the sin formula in column 2
plot(tbl.eredmeny, 'b-')
title('tbl.eredmeny', 'FontSize',fontSize);
grid on;
yline(0, 'LineWidth',3); % Draw a y axis.

% Print out the max and min
fprintf('Max Value = %f, min value = %f.\nNumber of rows in table = %d\n', max(tbl.eredmeny), min(tbl.eredmeny), height(tbl));

Max Value = 4.999996, min value = -5.000000.
Number of rows in table = 3142

%----------------------------------------------------------------------------------------------------------
function tbl = f91()
t = linspace(0, pi, 3142);
numRows = numel(t);
eredmeny = 5 * sin(3 * exp(t(:)));
et = cell(numRows, 1);
for k = 1 : numRows
    switch round(abs(eredmeny(k)))
        case 1
            et{k} = 'elegtelen';
        case 2
            et{k} = 'elegséges';
        case 3
            et{k} = 'kozepes';
        case 4
            et{k} = 'jo';
        case 5
            et{k} = 'jeles';
        otherwise
            et{k} = 'elegtelen';
    end     
end     

tbl = table(t(:), eredmeny, et, 'VariableNames', {'ido', 'eredmeny', 'ertekeles'});

end

However if by "not working" you meant something else, say what it is. Did you call the function from a script, or did you just click the green run triangle?

Perhaps the numbers from -5 to 5 should be generated by rand rather than that trig function you used.

eredmeny = -5 * 10 * rand(numRows, 1);

Did your task say specifically to use that, or was it just there from that other code you copied?