# Rafael Hernandez-Walls

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

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Solved

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

Solved

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

Solved

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

Solved

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

Solved

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

Solved

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

Solved

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

Solved

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

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 ...

9 months ago

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

Solved

mathematics , probability problem

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

1 year ago

Solved

MATLAB Basics: Complex Conjugates

For a given complex number, x, return the complex conjugate, y.

1 year ago

Solved

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

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: ...

1 year 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...

1 year 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...

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

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

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

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

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

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)...

2 years ago | 0

| accepted