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# Rafael Hernandez-Walls

##### Last seen: 6 days ago
1,139 total contributions since 2010

My interest is everything related to numerical schemes applied to PDE and Oceanography, UABC.

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MinMax mapping
Given a matrix, map all the elements within a given interval. For example, a=[ 2 5 10] mapped in the interval [1,2] ...

6 days ago

Solved

Rescale Scores
Each column (except last) of matrix |X| contains students' scores in a course assignment or a test. The last column has a weight...

6 days ago

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Find the Best Hotels
Given three input variables: * |hotels| - a list of hotel names * |ratings| - their ratings in a city * |cutoff| - the rat...

6 days ago

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Crop an Image
A grayscale image is represented as a matrix in MATLAB. Each matrix element represents a pixel in the image. An element value re...

6 days ago

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Calculate a Damped Sinusoid
The equation of a damped sinusoid can be written as |y = A.&#8519;^(-&lambda;t)*cos(2πft)| where |A|, |&lambda;|, and |f| ...

6 days ago

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Verify Law of Large Numbers
If a large number of fair N-sided dice are rolled, the average of the simulated rolls is likely to be close to the mean of 1,2,....

6 days ago

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Calculate BMI
Given a matrix |hw| (height and weight) with two columns, calculate BMI using these formulas: * 1 kilogram = 2.2 pounds * 1 ...

6 days ago

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Find the average of a random sequance
Write a function that generates random integers within a loop, and calculates the mean of the positive numbers only. At each ...

9 days ago

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Horizontal matrix sort
Given a matrix x with n rows and m columns, return a matrix y with n rows and 2m columns, such that every row in x is sorted fro...

9 days ago

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Find the index of nth maximum of a row vector of real numbers
Given a vector of real numbers x, find the index idx of _n_ th maximum value. If nth maximum occurs more than once, return the i...

9 days ago

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Please check if calorie intake is less than 300 kcal.
I like eating some puddings and some chocolate cookies around 3 o'clock. However, I care about calorie intake. Please check whe...

9 days ago

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means
Calculate the arithmetic, the geometric and the harmonic mean of a given vector (with positive elements) and return them in a ve...

9 days ago

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Energy-Mass Equivalence
Given input enegy of the object, E, and constant c = 300,000,000, find the mass of the object.

9 days ago

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Repetition of matrices
*A is a bold matrix: [1 2 3; 4 5 6;7 8 9]* Given an integer 'n' , a matrix B exists such that has n copies of A in the row an...

22 days ago

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Plot Damped Sinusoid
Given two vectors |t| and |y|, make a plot containing a blue ( |b| ) dashed ( |--| ) line of |y| versus |t|. Mark the minimum...

1 month ago

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frame of the matrix
Given the matrix M, return M without the external frame.

1 month ago

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Calculate Amount of Cake Frosting
Given two input variables |r| and |h|, which stand for the radius and height of a cake, calculate the surface area of the cake y...

1 month ago

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How long does it take to run a bath?
Given the *volume flow rate* (volume/time) of a faucet and the *volume* of a bath tub, find the amount of time it takes to fill ...

2 months ago

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R2012b atan in Degrees
Return in degrees the atan result of inputs for all four quadrants. *Examples:* [x, y] Degrees 1 0 0 1 1 ...

2 months ago

finding all indices of a value in matrix
A=[2 2 3 ; 2 4 2; 2 3 2]; [r,c]=find(A==min(A))

2 months ago | 0

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Remove duplicated triangles
Input T is a triangulation (triplet list of indices -positive integers-, each index refering to a vertex number in a correspondi...

4 months ago

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Weighted moving average
x1=[1 2 1]; y1=[1 2 2 4 5 6 6 8]; Make function for weighted moving average. z(i)=(x1(i)*y1(i)+x1(i+1)*y1(i+1)+x1(i+2)*y1...

4 months ago

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Height of a right-angled triangle
Given numbers a, b and c, find the height of the right angled triangle with sides a and b and hypotenuse c, for the base c. If a...

4 months ago

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Separate even from odd numbers in a vector - with a loop
*Using a loop*, rearrange a vector of integers such that the odd numbers appear at the beginning, and even numbers at the end. T...

4 months ago

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Angle of triangle
For three unknown points a b c, given three sides ab bc ca, find three angles abc bca cab in radians. Your function should b...

4 months ago

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Find the Oldest Person in a Room
Given two input vectors: * |name| - user last names * |age| - corresponding age of the person Return the name of the ol...

4 months ago

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Compute Fibonacci Number
Compute the _n_-th Fibonacci Number f(0) = 0, f(1) = 1, f(2) = 1, f(3) = 2, ... f(42) = 267914296

4 months ago

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Given a 4x4 matrix, swap the two middle columns
If a = [1 2 3 4; 1 2 3 4; 1 2 3 4; 1 2 3 4]; then the result is ans = 1 3 2 4 1 3 2...

4 months ago

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Can we make a triangle?
Given three positive number, check whether a triangle can be made with these sides length or not. remember that in a triangle su...

4 months ago

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Divisible by 10
Pursuant to the <http://www.mathworks.com/matlabcentral/cody/problems/42404-divisible-by-2 first problem> in this series, this o...

4 months ago