Problem 44952. Find MPG of Lightest Cars

Created by Pooja Lalan

Solve Later

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Solve

Solution Stats

20955 Solutions
2788 Solvers

Last Solution submitted on Sep 20, 2021

Last 200 Solutions

Problem Comments

18 Comments

18 Comments

Show 15 older comments

Paul Hoffrichter on 2 Mar 2020

Never worked with Tables before. Does Cody offer any ways to debug?

Paul Hoffrichter on 2 Mar 2020

Answer: I am able to print intermediate results.

Arman Lalani on 19 Mar 2020

I am getting the answer but the order of elements in my vector doesn't match the required answer. How can I get it in the required order?

Hugo Ormo on 5 Apr 2020

I do not see why this does not work. It seems to work in the Workspace alright:
function mpg = sort_cars(N)
cars = load('cars.mat')
carsSorted = sortrows(cars,'Weight')
mpg = carsSorted.MPG(1:N)
end

Pooja Lalan on 7 Apr 2020

@Hugo, check syntax for load in the documentation https://www.mathworks.com/help/matlab/ref/load.html

Specifically, check what to expect when assigning output from load to a variable.

Hugo Ormo on 7 Apr 2020

ty @Pooja :)

Peter Chiappetta on 9 Apr 2020

I have been working at this for a bit and it seems like it should work, What am I missing?
function mpg = sort_cars(N)
load('cars.mat')
A = sortrows(cars,'Weight')
mpg=A(1:N,2)
end

Parinit Angadi on 17 Dec 2020

Good example of tables

Jose Daniel Pinzon Vivas on 26 Jan 2021

Forgot to load the cars the first time

Shahryar Shahid on 21 Apr 2021

When I try to load the cars.mat file using
load cars
or
load cars.mat
or
load("cars.mat")
I get the error
Error using load
Unable to read file 'cars.mat'. No such file or directory.
I would appreciate help in resolving this error!

Mohanad M. Marzouk on 30 Apr 2021

Worst test cases, if you want us to load 2 different tables then why are you loading them again in the test suite, then you didn't even pass enough arguments to the function in the test case. Thus, even when the solution have the right logic, it fails because of the poor test cases

Subham Khan on 7 Jun 2021

I did,
load cars.mat
cars=sortrows(cars,4)
mpg=cars(1:N,2)

though the output in test 2 seems correct. I get incorrect assertion. Requesting Help.

goc3 on 7 Jun 2021

The problem does not work as intended, as loading the .mat file does not work and the table is not passed to the function.
Nonetheless, the problem is solvable—one simply needs to copy some of the test-case commands into the solution function and indicate which data set is being loaded based on the input N.

FB on 25 Jun 2021

The "load cars.mat" has unknown directory ang gives the below error:
"Error using load
Unable to read file 'cars.mat'. No such file or directory."

while copying the few first lines from "Test 1", it passes. however that should not be the correct way as "Test 2" has different set.

anyone knows how to load the mat file on online Matlab cody?

C KAMALESWAR REDDY on 1 Aug 2021

function mpg = sort_cars(N)
wgt=[cars.Weight]' ;
mpg1=[cars.MPG]';
mpg2=zeros(1,length(wgt));
for i=1:length(wgt)
[wgt1 inx]=max(wgt);
mpg2(end-i+1)=mpg1(inx);
wgt(inx)=0;
end
mpg = mpg2(1:N);
end

The above code is my solution, but it is not compiling can anyone help me with this..

tim che on 4 Aug 2021

This problem needs correction.
It uses two different "cars" sets for testing the answer. These two sets have different values for MPG.
Please, correct me if I'm wrong

Deborah Johnson on 25 Aug 2021 at 17:11

I am having the same issue as 'FB' below. However, I used the code given under Test1 to load the cars.mat. The code is below.

My code passes the 1st test but not the 2nd test. Can someone please assist me.

function MPG = sort_cars(N)
load(fullfile(matlabroot, 'toolbox/stats/statsdemos', 'carbig.mat'));
Model = strtrim(string(Model));
cars = table(Model, MPG, Horsepower, Weight, Acceleration);
save cars.mat cars

sorted = sortrows(cars,4);
MPG = sorted(1:N,2)
MPG = MPG{:,:}
end

N=25

米雪林 on 11 Sep 2021 at 5:29

my code:
function mpg = sort_cars(N)
load cars.mat cars
X= sortrows(cars,4);
mpg=X(1:N,2);
end

I have tried the two tests correctly, but failed to submit…Can anyone help me…

Solution Comments

Solution 6514149

Solution 6434914

Solution 6094078

1 Comment

1 Comment

Dustin Lindner Daii on 11 Jul 2021

The problem states that the variable name is "mpg" but it is actually "MPG".

Solution 6014685

Solution 5999560

1 Comment

1 Comment

Melissa Niesen on 22 Jun 2021

Nice example of using tables.

Solution 5874910

1 Comment

1 Comment

Shivam Gupta on 30 May 2021

Guys, first of all sort the weight column of table in ascending order by sortrows function and proceed further.....
and one more thing don't forget to convert table into array by table2array function otherwise it will showing an error.

Solution 4823217

Solution 4469417

3 Comments

3 Comments

Enrico Michielan on 27 Dec 2020

Someone can help me with this problem? On my matlab desktop it run but on the online version it doesn't works. Thanks

Dyuman Joshi on 22 Feb 2021

Hello, kindly refrain from posting the whole solution completely. You can provide hints or point out mistakes to help others, but try not to give the entire solution.

jx zhang on 8 Mar 2021

try load cars.mat

Solution 3647338

1 Comment

1 Comment

Cai Cai on 13 Nov 2020

Meaningless

Solution 2625967

2 Comments

2 Comments

priyanka p on 15 Jul 2020

Please share your full code if you have done it. It will be really helpful.

Thanks in advance

adrieto on 20 Nov 2020

What's the function of this line?
mpg=mpg{:,:}

I tried it on Matlab desktop but I got an error. what type of variable is mpg? double?

4 Comments

4 Comments

Show 1 older comment

Diego Guisasola Plejo on 21 Apr 2020

I don't know why my solution is not working:

function mpg = sort_cars(N)
cars = load('cars.mat')
B = sortrows(cars,2)
mpg = B.MPG(1:N)
end

I tested it on the desktop version and it works flawlessly.
Any ideas, please?

Thanks in advance!

Derik Zhou on 7 May 2020

sortrows(cars, 2) supposed to be sortrows(cars, 4), Weight is on Column 4 I think.
Better be like this: sortrows(cars, 'Weight', 'ascend');

Tavish Pattanayak on 8 May 2020

mpg=mpg{:,:}

Add this to your code.

lin li on 20 Jul 2020

Hello.The output is expected to be a column vector, whereas your code returns a table. You may try extracting the vectors from the table, like this.
function mpg = sort_cars(N)
load cars.mat
W=sortrows(cars,'Weight')
mpg = W.MPG(1:N)
end

Solution 2213868

2 Comments

2 Comments

Gulo Mana on 16 Apr 2020

Comparison is equal, why assertion is failed?

Tavish Pattanayak on 8 May 2020

The output should be an array not a table.

Solution 2172277

3 Comments

3 Comments

Adetiloye Joseph Bamisebi on 24 Mar 2020

I do not understand why this code failed assertion test even though it yields the correct answer

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

Pooja Lalan on 7 Apr 2020

The output is expected to be a column vector, whereas your code returns a table.

Prasad Reddy on 28 Apr 2020

I tried for the solution nearly 20 ways but didn't work. finally took help from the Matlab community and compleated it

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Problem 44952. Find MPG of Lightest Cars

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Problem 44952. Find MPG of Lightest Cars

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