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# Rafael Hernandez-Walls

Last seen: 12 days ago Active since 2010

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

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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 ...

3 months ago

Solved

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

3 months 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...

3 months 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...

3 months 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...

3 months 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?

3 months 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; ...

3 months 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...

5 months 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...

5 months 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 ...

9 months ago

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

1 year ago | 0

Solved

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

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

how i can find the chessboard lines and draw on the main image with any solution

1 year ago | 0

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

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

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

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

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

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...

2 years ago | 0

| accepted