Write a function called freezing that takes a vector of numbers that correspond to daily low temperatures in Fahrenheit. Return numfreeze, the number of days with sub freezing temperatures (that is, lower than 32 F) without using loops. Here is an ex

This question is soft-locked: new answers that are equivalent to already posted answers may be deleted without prior notice.

Hello there, I am very new to Matlab and I am having trouble with this question. I understand how to make the function work for the given matrix in the problem. However, I cannot find out how to make it work for random temperature vectors. Would anyone mind giving me a hint or helping me out? Would be greatly appreciated. Thank you.

[the cyclist]

Upload your code here, and maybe some folks will give you some hints.

[Andrew Marttini]

So this is what I have so far. Its mostly just the code to solve for the vector thats given.

function numfreeze = freezing (n)
n = [45 21 32 31 51 12]
n1 = n(n<32)
numfreeze = numel(n1)
end

[Sai Swaroop Maram]

function numfreeze=freezing(T)
T(T<32)=1;
T(T>=32)=0;
numfreeze=sum(T);

Answer 1

[Stephan]

function numfreeze = freezing (n)
n1 = n(n<32)
numfreeze = numel(n1)
end

Dont overwrite n - it is an input argument

[Andrew Marttini]

wow... lol okay um thanks man. i cant believe thats why I was getting it wrong.

[Stephan]

ist easy sometimes, please accept useful answers

[Tahsin Hossain]

function numfreeze = freezing(A) 
n = logical(A(A<32));
numfreeze = sum(n); 
end

[Agamjyot Singh Chadha]

Using logical can create a bug. For example, if the array 'n' has a value of 0 in it. By using logical the value of the input 0 will be 0 in the array n when instead it should be 1, cause 0 is less than 32. Thus the final result after summing everything in n will get you the wrong answer.

[Walter Roberson]

Agamjyot is correct.

[Hari Kiran Tirumaladasu]

Tahsin Hossain,

Try this code,

function numfreeze = freezing(A)

n = (A<32);

numfreeze = sum(n);

[SOUMYAJIT MONDAL]

Hari Kiran

Your ans will come wrong.

numfrezee will sum the elements less than 32

so it will be 21+32+....

Answer 2

[Vineet Singhal]

function numfreeze = freezing(v)
a= length(v(v<32));
numfreeze =a;
end

[Lokesh Sahu]

function numfreez = freezing(x)
    numfreez = length (x (x<32)) ;
end

%you dont even need that a, just use numfreez directly

[THIERNO AMADOU MOUCTAR BALDE]

it is working thanks

Answer 3

[Nadeem U Rehman]

function numfreeze = freezing(A)
F = A(A<32);
[row column] = size(A);
if size(A) == [1 column]
    numfreeze = size(F,2);
else
    numfreeze = size(F,1);
end
end

[Nadeem U Rehman]

%modified applicable to (nxm) matrices/column and row vectors:
function numfreeze = freezing(A)
F = A(A<32);
[row column] = size(A);
if size(A)== [row column]
    numfreeze = sum(A(:)<32);
end
end

[Rik]

What is that if supposed to do? Did you read the documentation for if to see how it handles array inputs?

And why did you delete your previous answer and proceed to post a new one without answering my question why you are posting these in the first place?

[Nadeem U Rehman]

i get feed back from people that know better than me, helps in learning. i deleted the previous one because you helped in figuring out the limited application of my code. Thank you!

please, tell me where i went wrong in this code.

i am new to MATLAB/Coding!

[Rik]

These homework solutions are probably not the best place to get feedback. After completing the Onramp tutorial (which is provided for free by Mathworks), I would suggest looking at this thread.

And where you went wrong is in assuming what == does, instead of reading the documentation. There is an important difference between equals (which is called when you write ==) and isequal. size(A)==[row column] will result in a two-element logical vector if A is a vector or 2D array (and an error if A has more dimensions).

% Let's take a look at what if does:
A=[];           if A, disp(A),end
A=true;         if A, disp(A),end

   1

A=[true false]; if A, disp(A),end
A=[true true];  if A, disp(A),end

   1   1

A=[false true]; if A, disp(A),end
A=[false false];if A, disp(A),end

Did you expect these results? What does this say about how your code would work?

Answer 4

[mohammad elyoussef]

function b = freezing(a)
f = a < 32;
b = sum(f);

Answer 5

[Yash Agarwal]

function numfreeze = freezing(A)
B = A(A<32);
numfreeze = size(B,2);
end

[Rik]

You are not promissed A is a either a row or column vector, so your solution should support both input types.

Answer 6

[Rajeev Mehndiratta]

function numfreeze = freezing(V)
A=0
V
V(V<32) = A
A =logical(V)
B=sum(A)
numfreeze=B
end

[Rik]

You're correct, this solution didn't exist in this thread yet, although I would clean it up to this:

function numfreeze = freezing(V)
V(V<32) = 0;
V = logical(V);
numfreeze = sum(V);
end

Answer 7

[Mohamed]

well, you can use the size function to determine the number of the aviable elements:

function output= freezing(x)
x_1=x(x<32); % it will output any number less than 32 of the given matrix
[b,output=size(x_1);  % b will equal to the unwanted elements (rows), output will equal to the number of the wanted number ( coloumbs)

%it can be vise versa if its a coloumb matrix%

[John D'Errico]

This is identical to at least one other solution already posed, except for one problem. Your code will fail due to a syntax error.

[DGM]

What's more remarkable is that the answer which this most closely duplicates had already been explained to be problematic. If I recall, the deleted version would have been a more appropriate comparison, but don't trust my recollection too much. These threads are all starting to blend together.

To reiterate and address what's been said in other comments, the question does not specify the vector orientation. Any decent solution should work for any vector orientation. When I say any orientation, I mean any array with only one non-singleton dimension.

Furthermore; the question text does vaguely suggest the use of array inputs. Since there's no good reason that a solution can't be generalized to support any N-D numeric array, then it's my opinion that it should. Such a solution would also support any vector.

So what are the problems with this example? Besides the missing bracket, The misuse of size() will result in the function silently returning incorrect results for anything other than a vector oriented along dim2 or higher. The fact that this actually works for higher-dim vectors was almost certainly nothing more than an accident based on a common misunderstanding of how size() works.

x = randi([0 64],100,1); % a column vector
freezing(x) % wrong output

ans = 1

x = reshape(x,1,[]); % a row vector
freezing(x) % correct output

ans = 51

x = reshape(x,1,1,[]); % a vector on dim3
freezing(x) % output is accidentally still correct

ans = 51

x = reshape(x,10,10); % a matrix
freezing(x) % wrong output

ans = 1

function output = freezing(x)
    x_1 = x(x<32);
    [~, output] = size(x_1); % tilde works here since R2009b
end

You could fix the problem:

function output = freezing(x)
    x_1 = x(x<32);
    output = numel(x_1);
end

... but that answer has already been posted, and it can still be simplified further anyway. I should also point out that the (likely autograded) assignment clearly specifies what the output variable name should be.

function numfreeze = freezing(x)
    numfreeze = nnz(x<32);
end

Note now that not only is this version simpler, it's also more generalized.