Rafael Hernandez-Walls

Last seen: ungefär 2 månader ago | Active since 2010

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

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Swap between first and last column
The idea is to swap between first and last column Ex = [1 2 3 4 5; 1 2 3 4 5; 1 2 3 4 5; 1 2 3 4 5; 1 2 3 ...

8 månader ago

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Remove a specific row with max value
Remove the row that contain the max value in the matrix? If you like the problem, please like it :)

8 månader ago

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Swap between rows
The idea is to swap between second and second last row Ex = [1 2 3 4 5; 5 4 3 2 1; 1 2 3 4 5; 1 2 3 4 5; ...

8 månader ago

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Count consecutive 0's in between values of 1
So you have some vector that contains 1's and 0's, and the goal is to return a vector that gives the number of 0's between each ...

11 månader ago

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Molar Air Density from Temperature and Pressure
The molar density of air can be found from the Temperature and Pressure using the ideal gas law. where the Molar density STP ...

ungefär 2 år ago

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Calculate Wind Chill Factor
The NWS Wind Chill Temperature (WCT) index formula for calculating the dangers from winter winds and freezing temperatures: Cal...

ungefär 2 år ago

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Air Mass to Star for an Observer at Mean Sea Level
Air mass is a measure of how much atmosphere light from a source above the atmosphere (eg sun, planet, star) has to travel throu...

ungefär 2 år ago

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Find Air Temperature from Cricket Stridulation Rate
Stridulation is the process that creates a cricket's “chirp” by rubbing their wings or legs. According to the Old Farmer's Alma...

ungefär 2 år ago

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Construyendo matrices parte 2
Construye la siguiente matriz a partir de otros tres vectores/matrices. [ 1 8 15 3 3 3 3 2 9 16 3 3...

ungefär 2 år ago

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Sum of series IV
What is the sum of the following sequence: Σ(-1)^(k+1) (2k-1)^2 for k=1...n for different n?

ungefär 2 år ago

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Back to basics 22 - Rotate a matrix
Covering some basic topics I haven't seen elsewhere on Cody. Rotate the input matrix 90 degrees counterclockwise (e.g. [1 2; ...

ungefär 2 år ago

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Composite Trapezoidal Rule for Numeric Integration
Use the trapezoidal rule to numerically integrate a function, _f(x)_, passed as the first argument, between upper and lower limi...

mer än 2 år ago

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Differential equations I
Given a function handle |f| an initial condition |y0| and a final time |tf|, solve numerically the differential equation dy...

mer än 2 år ago

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Weighted Convolution
Given two input vectors x = [x_1, x_2, ..., x_K] and y = [y_1, y_2, ..., y_K] of equal length, compute the weighted convolution ...

mer än 2 år ago

Answered
Determine if any key is being pressed
If only use the function: pause

ungefär 3 år ago | 0

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The Piggy Bank Problem
Given a cylindrical piggy bank with radius g and height y, return the bank's volume. [ g is first input argument.] Bonus though...

mer än 3 år ago

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mathematics , probability problem
How many different result can we have, rolling k dice?

mer än 3 år ago

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MATLAB Basics: Complex Conjugates
For a given complex number, x, return the complex conjugate, y.

mer än 3 år ago

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MATLAB Basics: Complex Numbers
For a given complex number, x, return the real and imaginary parts as a vector, y = [Real Imaginary].

mer än 3 år ago

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Flip coins

mer än 3 år ago

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Normalizing a vector

mer än 3 år ago

Solved

Return fibonacci sequence do not use loop and condition
Calculate the nth Fibonacci number. Given n, return f where f = fib(n) and f(1) = 1, f(2) = 1, f(3) = 2, ... Examples: ...

mer än 3 år ago

Solved

Number of Even Elements in Fibonacci Sequence
Find how many even Fibonacci numbers are available in the first d numbers. Consider the following first 14 numbers 1 1 2...

mer än 3 år ago

Solved

Find the next Fibonacci number
In the sequence of Fibonacci numbers, every number is the sum of the two preceding ones: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55...

mer än 3 år ago

Answered
matlab not plotting graph
You need one point in the equation of z h = [2,4,6,8,10]; x = 10.1; y = 2.5; z = (x * h.^2 - x - sqrt(y^2*h.^2 - y^2))./ (h....

mer än 3 år ago | 0

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Mass Conversion 1

mer än 3 år ago

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how i can find the chessboard lines and draw on the main image with any solution
Maybe you can use the Radon Transform, like this link: https://www.mathworks.com/help/images/detect-lines-using-the-radon-trans...

mer än 3 år ago | 0

Answered
how can I get y which correspond to x and then plot (x,y)??
Try this: x=linspace(-4,4); for r=1:length(x) y(r)=fzero(@(y)y.^3+0.2*exp(-1*x(r).^2)*y.^2-2.2039*y.^2+0.8155,1); end p...

mer än 3 år ago | 0

Answered
How to read data from text file and store as it is with variables
Assuming you have a file with only following line (name of file= 'algo.txt'): phi1_32_1 = 1 You could then read the line with...

mer än 3 år ago | 0

Answered
numerical simulation of travelling wave of epidemic model
try this.... clear all; xl=0; xr=1; %domain[xl,xr] J=1000; % J: number of dividion for x dx=(x...

mer än 3 år ago | 0

Rafael Hernandez-Walls

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