Problem 44952. Find MPG of Lightest Cars

Created by Pooja Lalan

Solve Later

{"relationships":[{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/document","targetMode":"","relationshipId":"rId1","target":"/matlab/document.xml"},{"relationshipType":"http://schemas.mathworks.com/matlab/code/2013/relationships/output","targetMode":"","relationshipId":"rId2","target":"/matlab/output.xml"}],"parts":[{"partUri":"/matlab/document.xml","relationship":[],"contentType":"application/vnd.mathworks.matlab.code.document+xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n<w:document xmlns:w=\"http://schemas.openxmlformats.org/wordprocessingml/2006/main\"><w:body><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>The file</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>cars.mat</w:t></w:r><w:r><w:t> contains a table named</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>cars</w:t></w:r><w:r><w:t> with variables</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>Model</w:t></w:r><w:r><w:t>,</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>MPG</w:t></w:r><w:r><w:t>,</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>Horsepower</w:t></w:r><w:r><w:t>,</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>Weight</w:t></w:r><w:r><w:t>, and</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>Acceleration</w:t></w:r><w:r><w:t> for several classic cars.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Load the MAT-file. Given an integer</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>N</w:t></w:r><w:r><w:t>, calculate the output variable</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>mpg</w:t></w:r><w:r><w:t>.</w:t></w:r></w:p><w:p><w:pPr><w:pStyle w:val=\"text\"/></w:pPr><w:r><w:t>Output</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>mpg</w:t></w:r><w:r><w:t> should contain the</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>MPG</w:t></w:r><w:r><w:t> of the top</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>N</w:t></w:r><w:r><w:t> lightest cars (by</w:t></w:r><w:r><w:t> </w:t></w:r><w:r><w:rPr><w:rFonts w:cs=\"monospace\"/></w:rPr><w:t>Weight</w:t></w:r><w:r><w:t>) in a column vector.</w:t></w:r></w:p></w:body></w:document>"},{"partUri":"/matlab/output.xml","contentType":"text/xml","content":"<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\" ?><embeddedOutputs><metaData><evaluationState>manual</evaluationState><layoutState>code</layoutState><outputStatus>ready</outputStatus></metaData><outputArray type=\"array\"/><regionArray type=\"array\"/></embeddedOutputs>"}]}

Solve

Solution Stats

17091 Solutions
2195 Solvers

Last Solution submitted on Apr 15, 2021

Last 200 Solutions

Problem Comments

10 Comments

10 Comments

Show 7 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

Andres Felipe Villalba Cortes on 27 Dec 2020

load cars
a = [];
c = str2double(cars.Variables);
Mg2 = c(:,2);
h1 = c(:,4);
for s = 1:N
[w,q] = min(h1,[],'omitnan');
h1(q) = max(h1)+1;
a = [a;q];
end
mpg = Mg2(a)

end

Jose Daniel Pinzon Vivas on 26 Jan 2021

Forgot to load the cars the first time

Solution Comments

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

2 Comments

2 Comments

Cai Cai on 13 Nov 2020

Meaningless

Andres Felipe Villalba Cortes on 27 Dec 2020

load cars
a = [];
c = str2double(cars.Variables);
Mg2 = c(:,2);
h1 = c(:,4);
for s = 1:N
[w,q] = min(h1,[],'omitnan');
h1(q) = max(h1)+1;
a = [a;q];
end
mpg = Mg2(a)

end

Solution 2625967

3 Comments

3 Comments

Umur Ulas Harman on 28 Jun 2020

it does not work if u did not put curly brackets. since otherwise u call a table. however, you need a column array to pass the test I believe.

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

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?

Solution 2581435

1 Comment

1 Comment

Piero Cimule on 19 Jun 2020

load cars.mat
sorted = sortrows (cars,4)
n = N
mpg = sorted(1:n,2)
mpg=mpg{:,:}

Solution 2263926

1 Comment

1 Comment

Tavish Pattanayak on 8 May 2020

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

Gives the correct output yet assertion failed. Why?

Solution 2226515

1 Comment

1 Comment

Diego Guisasola Plejo on 21 Apr 2020

This is an improved version of my code but still doesn't work:

function mpg = sort_cars(N)
S = load('cars.mat');
cars = struct2table(S)
B = sortrows(cars,2)
mpg = B.MPG(1:N)

end

Solution 2226463

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

Problem Recent Solvers2195

Problem Tags

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Problem 44952. Find MPG of Lightest Cars

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers2195

Suggested Problems

More from this Author13

Problem Tags

Community Treasure Hunt

Problem 44952. Find MPG of Lightest Cars

Solution Stats

Last 200 Solutions

Problem Comments

Solution Comments

Problem Recent Solvers2195

Suggested Problems

More from this Author13

Problem Tags

Community Treasure Hunt

Players