Solution 2226463

Submitted on 21 Apr 2020

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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

Test Suite

Test	Status	Code Input and Output
1	Fail	N = 5 load(fullfile(matlabroot, 'toolbox/stats/statsdemos', 'carbig.mat')); Model = strtrim(string(Model)); cars = table(Model, MPG, Horsepower, Weight, Acceleration); save cars.mat cars assert(isequal(sort_cars(N),[35; 31; 39.1; 35.1; 31])); N = 5 cars = struct with fields: cars: [406×5 table] Error using matlab.internal.math.sortrowsParseInputs Column sorting vector must contain integers with absolute value between 1 and the number of columns in the first argument. Error in sortrows (line 64) [col, nanflag, compareflag] = matlab.internal.math.sortrowsParseInputs(ismatrix(A),size(A,2),A,varargin{:}); Error in sort_cars (line 3) B = sortrows(cars,2) Error in Test1 (line 6) assert(isequal(sort_cars(N),[35; 31; 39.1; 35.1; 31]));
2	Fail	N = 6 load(fullfile(matlabroot, 'toolbox/stats/statsdemos', 'carsmall.mat')); Model = strtrim(string(Model)); cars = table(Model, MPG, Horsepower, Weight, Acceleration); save cars.mat cars assert(isequal(sort_cars(N),[33; 29.5; 26; 29; 38; 32])); N = 6 cars = struct with fields: cars: [100×5 table] Error using matlab.internal.math.sortrowsParseInputs Column sorting vector must contain integers with absolute value between 1 and the number of columns in the first argument. Error in sortrows (line 64) [col, nanflag, compareflag] = matlab.internal.math.sortrowsParseInputs(ismatrix(A),size(A,2),A,varargin{:}); Error in sort_cars (line 3) B = sortrows(cars,2) Error in Test2 (line 6) assert(isequal(sort_cars(N),[33; 29.5; 26; 29; 38; 32]));

Test

Status

Code Input and Output

Fail

N = 5 load(fullfile(matlabroot, 'toolbox/stats/statsdemos', 'carbig.mat')); Model = strtrim(string(Model)); cars = table(Model, MPG, Horsepower, Weight, Acceleration); save cars.mat cars assert(isequal(sort_cars(N),[35; 31; 39.1; 35.1; 31]));

N = 5 cars = struct with fields: cars: [406×5 table]

Error using matlab.internal.math.sortrowsParseInputs Column sorting vector must contain integers with absolute value between 1 and the number of columns in the first argument. Error in sortrows (line 64) [col, nanflag, compareflag] = matlab.internal.math.sortrowsParseInputs(ismatrix(A),size(A,2),A,varargin{:}); Error in sort_cars (line 3) B = sortrows(cars,2) Error in Test1 (line 6) assert(isequal(sort_cars(N),[35; 31; 39.1; 35.1; 31]));

Fail

N = 6 load(fullfile(matlabroot, 'toolbox/stats/statsdemos', 'carsmall.mat')); Model = strtrim(string(Model)); cars = table(Model, MPG, Horsepower, Weight, Acceleration); save cars.mat cars assert(isequal(sort_cars(N),[33; 29.5; 26; 29; 38; 32]));

N = 6 cars = struct with fields: cars: [100×5 table]

Error using matlab.internal.math.sortrowsParseInputs Column sorting vector must contain integers with absolute value between 1 and the number of columns in the first argument. Error in sortrows (line 64) [col, nanflag, compareflag] = matlab.internal.math.sortrowsParseInputs(ismatrix(A),size(A,2),A,varargin{:}); Error in sort_cars (line 3) B = sortrows(cars,2) Error in Test2 (line 6) assert(isequal(sort_cars(N),[33; 29.5; 26; 29; 38; 32]));

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