Rafael Hernandez-Walls

Last seen: Today | 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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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...

19 days ago

Solved

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

19 days ago

Solved

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 ...

5 months ago

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

11 months 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...

1 year ago

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

1 year ago

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

1 year 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].

1 year ago

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Flip coins

1 year ago

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Normalizing a vector

1 year ago

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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: ...

1 year ago

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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...

1 year ago

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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...

1 year ago

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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....

1 year ago | 0

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Mass Conversion 1

1 year 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...

1 year ago | 0

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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...

1 year ago | 0

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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...

1 year ago | 0

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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...

1 year ago | 0

Answered
Read a txt file
try this Dens1 = [A(:,1),9.11*A(:,2).^(1.326)]; fileID1=fopen('E1.txt','w'); % [n,~]=size(Dens1); for k=1:n b=fprintf(...

1 year ago | 0

Answered
How to display correlation coefficents on plot?
you can try something like this: x = [0 0.000009 0.000018 0.000028 0.000037 0.000046 0.000055 0.000065 0.000074 0.000083 0.0000...

1 year ago | 0

Answered
extracting value from a matrix
I think it is better to put the variable X as a string and from there start. for example: X=['1000000000000000000000000000000...

1 year ago | 0

| accepted

Answered
How to get Taylor polynomial for functions?
You can use a function that is in the MAThWORKS fileexchange (I put the link): str=input('Function? ','s'); %tray with: cos(x)...

1 year ago | 0

| accepted

Answered
Change the sign of a Vector over N intervals
Use something like this: Y=rand(1,20); d=[1:4,8:12,17:20]; Y(d)=-Y(d)

1 year ago | 0

Answered
For loop only outputting the final value.
Try using something like this: t=linspace(0,3*pi,100) t=linspace(0,3*pi,100); for k=1:length(t) y = q2(t(k)); val...

1 year ago | 0

Answered
Plotting log x and y
Why don't you treat like this: n = 30; x = 0.5; h(1) = 1; emin = 1; for i =1:n if i==1 h(1)=0.5; else ...

1 year ago | 0

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Mass Conversion 2

1 year ago

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Calculate the answer to life the universe and everything
<https://en.wikipedia.org/wiki/42_(number)>

1 year ago

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How many hours are there in a day in Italy?
Remember "European Summer Time"

1 year ago

Solved

Temperature Conversion 3

2 years ago

Rafael Hernandez-Walls

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