Rafael Hernandez-Walls

Last seen: 3 days ago

1,281 total contributions since 2010

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

Rafael Hernandez-Walls's Badges

Answered
Why does my plot not appear?
Vmax = 354*10^(-6); Km = 1.5*10^(-3); S = .0000005:.0000005:.000030; v = Vmax*S./(Km + S); plot(S,v);

4 days ago | 0

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Multiple Iterations over a system of linear equations
I think the problem is where the plot function, maybe you need to put another command to plot in each iteration, something like ...

10 days ago | 0

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for loop and if-statement
This may help you Time=[0.5 1.51 2.6 3.65 4.71 6.8 7.9 9.1 10.3 11.1 12.3 15 16.2 17.3 18.5 19.6]; dife=diff(Time); heelstrik...

12 days ago | 0

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Solved

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

21 days ago

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Diagonal Pattern
For a positive integer |n|, return an |nXn| matrix |mat| such that the value of each element in row |i| and column |j| is given ...

21 days ago

Answered
"Z must be a matrix, not a scalar or vector." PLEASE HELP!
x1 = 1:.1:4; x2 = 1:.1:4; [X,Y] = meshgrid(x1,x2); Z= ps2func(X,Y); mesh(X,Y,Z) grid on hold on function [f]=ps2func(x...

1 month ago | 1

Answered
Converting Euler's method calculation into matlab
tray this: % Initial conditions and setup Q=400; A=1200; alph=160; h = 0.5; % step size t = 0:0.5:10; % the range of t ...

1 month ago | 1

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Answered
Lotka-Volterra Predatir Prey Model Code
using this: function [dPdt] = lotkavolterra(t,P) alpha = 1.5; % you have error here: you using alpa beta = 1; gamma = 3; de...

1 month ago | 0

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Solved

Counting Sequence
Given a vector x, find the "counting sequence" y. A counting sequence is formed by "counting" the entries in a given sequence...

2 months ago

Answered
¿Por qué mi código no corre?
Hola, Creo que tu condicion incial debe ser de solo dos elementos y no de tres. Intenta este programa principal, el cual llamará...

2 months ago | 0

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Triangle of numbers
Create a matrix with the integers from 1 to |n| arranged in a triangular shape. Every row |i| of the matrix contains |i| inte...

2 months ago

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How do I plot a function that has been split into multiple time intervals
I don't know if I understand your problem, but I think it is related to the way to program the following code: t=-1:0.1:6; y...

2 months ago | 0

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Back to basics 2 - Function Path
Covering some basic topics I haven't seen elsewhere on Cody. Given a string that is the name of a MATLAB function, return a s...

2 months ago

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Prime factor digits
Consider the following number system. Calculate the prime factorization for each number n, then represent the prime factors in a...

2 months ago

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How do I display squares of all even integers from zero to some positive integer input by the the user.And the program must continuously request a number from the user untill a valid a positive integer is entered
M=input('enter integer:'); for c=0:M if mod(c,2)==0 c^2 end end

2 months ago | 0

Answered
hi I am trying to calculate the 4th root of the function f(x)=3x4+7x3−4x2−10x+15 using newtons method and a for - loop
clear clc close all % function f = @(x) 3*x.^4 + 7*x.^3 - 4*x.^2 - 10*x + 1/5; % derivative df = @(x) 12*x.^3 + 21*x.^2...

2 months ago | 0

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Making combinations using random number generators
N=input('give me number of random elements:'); a=input('lower limit of the numbers to generate:'); b=input('upper limit of the...

2 months ago | 0

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How to create a noisy signal for wavelet transform practice?
maybe this code will help you N=1000; x=linspace(0,2*pi,N); y=sin(x); y2=randn(1,N); y3=y+y2*.1; subplot(2,1,1);plot(x,y)...

2 months ago | 1

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Solved

Given a matrix A return a vector of the product of the elements in each column using a loop without using prod.
--------------------- for m: 3 1 3 3 10 1 9 1 9 4 1 4 5 6 5 ...

2 months ago

Solved

Product of Each Column
Given a matrix |mat| with |n| columns, return a row vector |v| of length |n|, where every element in |v| is the product of the |...

2 months ago

Solved

Replace Nonzero Numbers with 1
Given the matrix x, return the matrix y with non zero elements replaced with 1. Example: Input x = [ 1 2 0 0 0 ...

2 months ago

Answered
Euler's Method
for n = [10, 20, 40, 80, 160] a = 0; b = .5; c = .25; x = linspace(a,b,n);%[a:n+1:b]; f = x.^3; dx = x(...

2 months ago | 0

Answered
plotting for cosine wave
I change some lines.... N=45; theta=0:360; % range of values of theta Na1=2*N*cosd(theta); % cosd for cos when you use de...

3 months ago | 0

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Solving a simple integral with input equation from user
syms x str = input('Enter an equation in x: ','s') ; f = function_handle.empty; f = eval(['@(x)', str]); %x = f(); xmin= ...

3 months ago | 1

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Solved

Area of a pentagon
Given the side of a regular pentagon and its apothem return the area of pentagon. Remember the area of pentagon is calculate ...

3 months ago

Solved

Find the area of the square
There are *n²* circles inscribed in the square ABCD. The perimeter of each circle is *aπ* <<http://imgfz.com/i/3wzCeAT.png>> ...

3 months ago

Solved

Times 5
Try out this test problem first. Given the variable x as your input, multiply it by five and put the result in y. Examples...

3 months ago

Solved

Times 10
Try out this test problem first. Given the variable x as your input, multiply it by ten and put the result in y. Examples:...

3 months ago

Solved

Doubling elements in a vector (★★)
(copy of prob. 1024) Given the vector A, return B in which all numbers in A are doubling. So for: A = [ 1 5 8 ] t...

3 months ago

Solved

Mo money, mo math #2! (★★★)
(adapted from Prob 9 Cody team) You have a matrix for which each row is a person and the columns represent the number of quar...

3 months ago