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Mayla
Last activity on 19 Sep 2023

Problem 1899. Convert a Cell Array into an Array

Thats the task:

Given a square cell array:

x = {'01', '56'; '234', '789'};

return a single character array:

y = '0123456789'

I wrote a code that passes Test 1 and 2 and one that passes Test 3 but I'm searching a condition so that the code for Test 3 runs when the cell array only contains letters and the one for Test 1 and 2 in every other case. Can somebody help me?

This is my code:

 y = []
[a,b]=size(x)
%%TEST 3
delimiter=zeros(1,a)
delimiter(end)=1
delimiter=repmat(delimiter,1,b)
delimiter(end)=''
delimiter=string(delimiter)
y=[]
for i=1:a*b
      y = string([y x(i)])
end
y=join(y,delimiter)
y=erase(y,'0')
y=regexprep(y,'1',' ')
%%TEST 1+2
for i=1:a*b
      y = string([y x(i)])
      y=join(y)
  end
  y=erase(y,' ' )

Hans Scharler
Last activity on 14 Sep 2023

22 Years of the MATLAB Central community!

Here's a screenshot from 22 years ago. Thanks for building one of the best engineering and science communities together.

anniversary

Mayla
Last activity on 13 Sep 2023

Problem 2022. Find a Pythagorean triple

That's the question: Given four different positive numbers, a, b, c and d, provided in increasing order: a < b < c < d, find if any three of them comprise sides of a right-angled triangle. Return true if they do, otherwise return false .

I wrote this code but it doesn't pass test 7. I don't really understand why it isn't working. Can somebody help me?

function flag = isTherePythagoreanTriple(a, b, c, d)
a2=a^2
b2=b^2
c2=c^2
d2=d^2
format shortG
  if a2+b2==c2
      flag=true
  else if a2+b2==d2
          flag=true      
  else if a2+c2==d2
           flag=true
  else if c2+b2==d2
           flag=true
  else flag=false
  end
  end
  end
  end
end

Mayla
Last activity on 24 Oct 2023

Problem 44952. Find MPG of Lightest Cars

That's the question:

The file cars.mat contains a table named cars with variables Model, MPG, Horsepower, Weight, and Acceleration for several classic cars.

Load the MAT-file. Given an integer N, calculate the output variable mpg.

Output mpg should contain the MPG of the top N lightest cars (by Weight) in a column vector.

I wrote this code and the resulting column vector has the right values but it doesn't pass the tests. What's wrong?

function mpg = sort_cars(N)
load cars.mat
sorted=sortrows(cars,4)
mpg = sorted(1:N,2)
end

Image Analyst
Last activity on 22 Jul 2024

My preferred vacation is to visit

cities

15%

beaches, islands, or cruises

22%

rivers, lakes, or mountains

33%

National Parks or historical sites

14%

wherever my family lives

12%

somewhere else

13709 votes

Nitin Daniel
Last activity on 4 Sep 2023

MPC for EV thermal management

I am trying to make a simulink model to use a MPC to reduce power consumption of HVAC system in an electric vehicle during cool down from ambient temperature to a set point temperature. Any help regarding this would be appreciated

power-electronics-control

Ali
Last activity on 3 Aug 2023

Transfer function has 5th order denominator, how to factor the denominator such as D(s) = (1+s/wp) (1+s/wo1Q1 + (s/wo1)²) (1+s/wo2Q2 + (s/wo2)²)

Hi Everyone,

I have a high-order filter and I need to determinate its R,L,C values. In the simulation, the filter is unstable for some values. But I want to find values for stability of the filter. For second order system has some formulation between Q and phase margin so that it can be obtain the stability ciriteria to choose components.

My transfer function denominator is 5th order polynomial, and it is not possible to find roots in terms of R,L,C, Lm. I need to factor it like one 1th and two second order as shown in below.

D(s) = (1+s/wp) (1+s/wo1Q1 + (s/wo1)²) (1+s/wo2Q2 + (s/wo2)²)

Is there any methods to reduce order of transfer function?(Maybe, it can be possible for only in certain frequency range, can be renounced high-frequency )

https://www.mathworks.com/matlabcentral/profile/authors/951521

Toshiaki Takeuchi
Last activity on 31 Jul 2023

Any interest in getting interviewed?

Hello, an intern working at MathWorks is finishing up his program soon and he would like to interview some MATLAB users. He is looking for people who can give their perspective on the question:

"What makes MATLAB and Simulink special in comparison to other languages?"

Ultimately he plans to condense the answers into 15-second videos or sound bites.

If people are willing to participate but want more time to talk about their experience with MATLAB, he doesn't have time left for in-depth interviews but he can find someone else to take over the project.

Please send me an email via my profle if you are interested.

interview

Image Analyst
Last activity on 1 Dec 2023

If you were EXTREMELY wealthy, would you still work?

Yes, in my company that I own

35%

Yes, for someone else (or Univ.)

21%

Only for free, for charities

13%

Only in my charitable foundation

No, I'd just play, travel, & relax

25%

15668 votes

Sunday Olayanju
Last activity on 22 Aug 2023

My state space model of VSI inverter with SVPWM won't produce output voltage and current in abc!

Kindly help me correct this code to function properly. I am just learning MATLAB. i cannot get the output in abc frame. This is the code:

%----------- Define input and state parameters-----------------------------

clc

v_dc = 350; % DC input voltage in V

m = 0.841; % modulation index

C = 4000e-6; % DC buss capacitance in uf

L_1 = 2.5e-3; % Inverter side inductance in mH

L_2 = 2.5e-3; % Load side inductance in mH

L = 0; % load inductance

C_f = 10e-6; % filter capacitance in uf

R_f = 0.7; % damping resistance in ohms

R_L = 20; % load resistance in ohms

f_s = 10e3; % switching frequency

f = 60; % System frequency

R_s = 0.01; % Capacitance of the DC circuit

I_d = 8.594; % steady state current

w = 2*pi*f; % System angular Frequency

% Define initial steady state values

v_c = 349.4; i_d = 8.594; i_q = -0.213; v_df = 285; v_qf = -120; i_Ld = 8.594; i_Lq = 0.85;

%------------------S V P W M Generator-------------------------------------

% Define reference vector Uref

U_mag = m*v_dc/2; % Magnitude of Uref

% Define switching vectors

U1 = [v_dc/2;0]; % Vector Q1

U2 = [v_dc/4;sqrt(3)*v_dc/4]; % Vector Q2

U3 = [-v_dc/4;sqrt(3)*v_dc/4]; % Vector Q3

U4 = [-v_dc/2;0]; % Vector Q4

U5 = [-v_dc/4;-sqrt(3)*v_dc/4]; % Vector Q5

U6 = [v_dc/4;-sqrt(3)*v_dc/4]; % Vector Q6

% Define sector angles

theta1 = pi/6;

theta2 = pi/2;

theta3 = 5*pi/6;

theta4 = 7*pi/6;

theta5 = 3*pi/2;

theta6 = 11*pi/6;

% Define duty cycles for each switch using a for loop

for t=0:1/f_s:1/f % Time variable from 0 to one cycle of system frequency with steps of switching frequency

U_phase = w*t; % Phase of Uref (t is time variable)

U_alpha = U_mag*cos(U_phase); % Alpha component of Uref

U_beta = U_mag*sin(U_phase); % Beta component of Uref

if (0 <= U_phase) && (U_phase < theta1) % Sector 1

T1 = (sqrt(3)*U_beta + U_alpha)/(2*v_dc);

T2 = (-sqrt(3)*U_beta + U_alpha)/(2*v_dc);

T0 = 1 - T1 - T2;

d_a(round(t)+1) = T1 + T0/2;

d_b(round(t)+1) = T2 + T0/2;

d_c(round(t)+1) = T0/2;

elseif (theta1 <= U_phase) && (U_phase < theta2) % Sector 2

T3 = (sqrt(3)*U_beta - U_alpha)/(2*v_dc);

T2 = (sqrt(3)*U_beta + U_alpha)/(2*v_dc);

T0 = 1 - T3 - T2;

d_a(round(t)+1) = T0/2;

d_b(round(t)+1) = T2 + T0/2;

d_c(round(t)+1) = T3 + T0/2;

elseif (theta2 <= U_phase) && (U_phase < theta3) % Sector 3

T3 = (sqrt(3)*U_beta - U_alpha)/(2*v_dc);

T4 = (-sqrt(3)*U_beta - U_alpha)/(2*v_dc);

T0 = 1 - T3 - T4;

d_a(round(t)+1) = T0/2;

d_b(round(t)+1) = T0/2;

d_c(round(t)+1) = T3 + T0/2;

elseif (theta3 <= U_phase) && (U_phase < theta4) % Sector 4

T5 = (-sqrt(3)*U_beta + U_alpha)/(2*v_dc);

T4 = (-sqrt(3)*U_beta - U_alpha)/(2*v_dc);

T0 = 1 - T5 - T4;

d_a(round(t)+1) = T5 + T0/2;

d_b(round(t)+1) = T0/2;

d_c(round(t)+1) = T4 + T0/2;

elseif (theta4 <= U_phase) && (U_phase < theta5) % Sector 5

T5 = (-sqrt(3)*U_beta + U_alpha)/(2*v_dc);

T6 = (sqrt(3)*U_beta + U_alpha)/(2*v_dc);

T0 = 1 - T5 - T6;

d_a(round(t)+1) = T5 + T0/2;

d_b(round(t)+1) = T6 + T0/2;

d_c(round(t)+1) = T0/2;

elseif (theta5 <= U_phase) && (U_phase < theta6) % Sector 6

T1 = (sqrt(3)*U_beta + U_alpha)/(2*v_dc);

T6 = (sqrt(3)*U_beta - U_alpha)/(2*v_dc);

T0 = 1 - T1 - T6;

d_a(round(t)+1) = T1 + T0/2;

d_b(round(t)+1) = T0/2;

d_c(round(t)+1) = T6 + T0/2;

end

%-------------------------Define system matrices---------------------------

% Create Three-phase SVPWM VSI Inverter

% System matrix Nx-by-Nx matrix

A = [-1/(C*R_s),-sqrt(3)*m/(2*C),0,0,0,0,0;

sqrt(3)*m/(3*L_1),-R_f/(3*L_1),w,-1/(2*L_1),-sqrt(3)/(6*L_1),-R_f/(3*L_1),0;

0,-w,-R_f/(3*L_1),-sqrt(3)/(6*L_1),-1/(2*L_1),0,R_f/(3*L_1);

0,1/(2*C_f),-sqrt(3)/(6*C_f),0,w,-1/(2*C_f),sqrt(3)/(6*C_f);

0,sqrt(3)/(6*C_f),1/(2*C_f),-w,0,-sqrt(3)/(6*C_f),-1/(2*C_f);

0,R_f/(3*(L_2+L)),0,1/(2*(L_2+L)),sqrt(3)/(6*(L_2+L)),((-3*R_L-R_f)/(3*(L_2+L))),w;

0, 0, R_f/(3*(L_2+L)), -sqrt(3)/(6*(L_2+L)), 1/(2*(L_2+L)), -w, ((-3*R_L-R_f)/(3*(L_2+L)))];

% Define input matrix

B = [1/(C*R_s),-sqrt(3)*i_d/(2*C);d_a*v_dc,(sqrt(3)*v_c)/L_1;d_b*v_dc,0;d_c*v_dc,0;0,0;0,0;0,0]; % Nx-by-Nu input matrix

% Define output matrix

C = [0 1 0 0 0 0 0; % Ny-by-Nx matrix

0 0 1 0 0 0 0;

0 0 0 1 0 0 0;

0 0 0 0 1 0 0;

0 0 0 0 0 1 0;

0 0 0 0 0 0 1];

% Feedthrough matrix

D = zeros(6, 2); % Ny-by-Nu matrix

% create state-space model object

sys = ss(A,B,C,D);

% Define initial conditions and input

x0 = [v_c; i_d; i_q; v_df; v_qf; i_Ld; i_Lq]; % Initial state vector

t = 0:1e-6:0.5; % Time vector for simulation

u = repmat([v_dc;m],1,length(t)); % repeat u for each time step

% Simulate the system

[y, ~, x] = lsim(sys, u, t, x0);

% Extract the states

v_c_sim = x(:, 1);

i_d_sim = x(:, 2);

i_q_sim = x(:, 3);

v_df_sim = x(:, 4);

v_qf_sim = x(:, 5);

i_Ld_sim = x(:, 6);

i_Lq_sim = x(:, 7);

% Extract the outputs

v_abc_sim = y(:, 1:3);

i_abc_sim = y(:, 4:6);

v_dq_sim = y(:, 4:5);

i_dq_sim = y(:, 2:3);

% Plot the variables

figure;

subplot(4, 2, 1);

plot(t, v_c_sim);

xlabel('Time');

ylabel('v_c');

title('Capacitor Voltage');

subplot(4, 2, 2);

plot(t, i_d_sim);

xlabel('Time');

ylabel('i_d');

title('d-Axis Current');

subplot(4, 2, 3);

plot(t, i_q_sim);

xlabel('Time');

ylabel('i_q');

title('q-Axis Current');

subplot(4, 2, 4);

plot(t, v_df_sim);

xlabel('Time');

ylabel('v_df');

title('d-Component Filter Voltage');

subplot(4, 2, 5);

plot(t, v_qf_sim);

xlabel('Time');

ylabel('v_qf');

title('q-Component Filter Voltage');

subplot(4, 2, 6);

plot(t, i_Ld_sim);

xlabel('Time');

ylabel('i_Ld');

title('d-Axis Load Current');

subplot(4, 2, 7);

plot(t, i_Lq_sim);

xlabel('Time');

ylabel('i_Lq');

title('q-Axis Load Current');

% Perform coordinate transformation from dq frame to abc frame for currents

i_a_sim = cos(w*t)*i_d_sim - sin(w*t)*i_q_sim;

i_b_sim = cos(w*t - 2*pi/3)*i_d_sim - sin(w*t - 2*pi/3)*i_q_sim;

i_c_sim = cos(w*t + 2*pi/3)*i_d_sim - sin(w*t + 2*pi/3)*i_q_sim;

% Perform coordinate transformation from dq frame to abc frame for voltages

v_a_sim = cos(w*t)*v_df_sim - sin(w*t)*v_qf_sim;

v_b_sim = cos(w*t - 2*pi/3)*v_df_sim - sin(w*t - 2*pi/3)*v_qf_sim;

v_c_sim = cos(w*t + 2*pi/3)*v_df_sim - sin(w*t + 2*pi/3)*v_qf_sim;

Many thanks

goc3
Last activity on 10 Jul 2023

I use MATLAB on x setups. (work, home; laptop, tablet; local installation, online; etc.)

33%

34%

18%

1643 votes

Image Analyst
Last activity on 19 Aug 2023

The glass is ...

half full.

12%

half empty.

both.

12%

twice as big as it needs to be.

15%

1/2 full of beer, 1/2 full of air.

17%

What glass???

39%

6618 votes

Joel Hottinger
Last activity on 16 Jun 2023

No longer able to rate difficulty of qustions on Cody

I recently have found that I am no longer able to give my difficulty rating for questions on Cody after sucessfully completing a question. This is obviously not a big deal, I was just wondering if this was an issue on my end or if there was some change that I was not aware of.

The option to rate does not pop up after solving a problem, and the rating in general does not even show up anymore when answering questions (though it is visible from problem groups).

cody

KALYAN ACHARJYA
Last activity on 3 Jul 2023

Will the MATLAB Answers community diminish/obsolete with the rise of AI-based chatbots?

The MATLAB Answers community is an invaluable resource for all MATLAB users, providing selfless assistance and support. However, with the emergence of AI-based chatbots, like chatGPT, there may be concerns about the future relevance and utility of the MATLAB Answer community. What are your thoughts?

Prakhar Rathore
Last activity on 13 Sep 2023

Electric vehicle thermal management

Hello, Recently I have started working on a thermal management project at my Institute. I am taking some hints from en example of EV thermal management provided by MATLAB. I am having an issue in deciding how the battery current and powertrain heat load is calculated as a function of vehicle speed. It would be helpful if someone could provide some links or references regarding this. (Also, attaching a screenshot of the example for better understanding)

Adam Danz
Last activity on 7 Oct 2024

Today, while using MATLAB, I'm going to....

figure out what my old code does

18%

write code comments for future me

11%

address a code analyzer warning

reflect on the skills I've gained

get food on my mouse and keyboard

38%

All of the above

22%

16434 votes

https://www.youtube.com/watch?v=Iu4M3dD0kPQ

Toshiaki Takeuchi
Last activity on 23 May 2023

YouTube Live Stream 5/25 @11:00 am EDT Getting Started with Simulink | Tips and Tricks to Get the Most Out of Simulink

Getting Started with Simulink | Tips and Tricks to Get the Most Out of Simulink

Watch live as Tianyi Zhu and Ashwin Dhawad walk through how you can get started with Simulink by modeling, simulating, and tuning a PID controller for a DC Motor. This session isn’t just for beginners; they will show you the latest and greatest tips and tricks to help you get the most out of Simulink.

Date & Time: May 25, 2023 at 11:00 am EDT (see time in your time zone)

Gurumoorthi K
Last activity on 30 May 2023

Sort Matlab table, monthly and seasonally. plot mean and trend seasonal map

I am processing ocean and climate data (1982-2022). Here, I have table which having heatwaves events details. Now, I want to sort the data month wise and also seasonal wise (summer:October- February, and winter:March-September), and then i wanted to plot mean seasonal and trend.

Sample file is attached. length of original file may vary in size.

Thanks in addvance.

distance-learning

Toshiaki Takeuchi
Last activity on 22 May 2023

MATLAB Central Community has a new API

MATLAB Central has been great community-based MATLAB resources, but you can now access its content programmatically via the public API, and I created a MATLAB function to take advantage of that. You can learn more here https://api.mathworks.com/community

Example:

data = searchMATLABCentral("plotting",scope="matlab-answers",sort_order="created desc",created_after=datetime("2023-01-01"));
T = struct2table(data.items);
T(:,["created_date","title","is_answered"])

Output

Function

function results = searchMATLABCentral(query,options)
% SEARCGMATLABCENTRAL retrieves content of the MATLAB Central for a given
% query and returns the result as a struct.
% The function uses MathWorks RESTful API to search for content.
% The API is rate limited via IP throttling. No authentication is required.
% See API documentation for more details https://api.mathworks.com/community
%
% Input Arguments:
%
%   query (string)            - Required. The search query string.
%   scope (string)            - Optional. Specify the artifact. If not specified,
%                               the scope defaults to 'matlab-answers'. 
%                               Other options include 'file-exchange','blogs','cody', 
%                               'community-highlights', and 'community-contests'.
%   tags (string)             - Optional. Specify a comma-separated list of tags. 
%   created_before (datetime) - Optional. Specify the last date in the results 
%   created_after (datetime)  - Optional. Specify the first date in the results
%   sort_order (string)       - Optional. Speficy the order of the results. 
%                               If not specified, it defaults to "relevance desc".
%                               Other options include 'created asc', 'created desc', 
%                               'updated asc','updated desc', 'relevance asc', 
%                               and 'relevance desc'.
%   page (integer)            - Optional. Specify the page to retrieve.
%                               If the 'has_more' field in the result is positive, 
%                               increment this argument to retrieve the next page.
%   count (integer)           - Optional. Specify the number of results as a value 
%                               between 1 and 50; The default is 10. 
%
% Output Arguments:
%
%   results (struct)          - Structure array containing the results of the search.
% validate input arguments
arguments
    query string {mustBeNonzeroLengthText,mustBeTextScalar}
    options.scope string {mustBeMember(options.scope,["matlab-answers", ...
        "file-exchange","blogs","cody","community-highlights", ...
        "community-contests"])} = "matlab-answers";
    options.tags string {mustBeNonzeroLengthText,mustBeVector}
    options.created_before (1,1) datetime 
    options.created_after (1,1) datetime
    options.sort_order string {mustBeMember(options.sort_order,["created asc", ...
        "created desc","updated asc","updated desc","relevance asc","relevance desc"])}
    options.page double {mustBeInteger,mustBeGreaterThan(options.page,0)}
    options.count double {mustBeInteger,mustBeInRange(options.count,1,50)}
end
% API URL and endpoint
url = "https://api.mathworks.com/community";
endpoint = "/v1/search";
% convert MATLAB datetime to the internet datetime format string
if isfield(options,"created_before")
    options.created_before = string(options.created_before,"yyyy-MM-dd'T'HH:mm:ss'Z'");
end
if isfield(options,"created_after")
    options.created_after = string(options.created_after,"yyyy-MM-dd'T'HH:mm:ss'Z'");
end
% convert optional inputs into a cell array of key-value pairs
keys = fieldnames(options);
vals = struct2cell(options);
params = [keys,vals].';
% call the API
try
    results = webread(url+endpoint,"query",query,params{:});
catch ME
    rethrow(ME)
end
end

community api