Ryo Ishido

Last seen: 4 meses ago | Active since 2018

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Easy Sequences 11: Factorial Digits without Trailing Zeros
Here is an easy one... It is not difficult to count the number of digits of the factorial of a given number. For example for 'n...

5 meses ago

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Easy Sequences 10: Sum of Cumsums of Fibonacci Sequence
The function F(n) is defined as the set of Fibonacci numbers from the first up to the n-th. S(n) is the result of applying to F,...

5 meses ago

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Easy Sequences 9: Faithful Pairs
A "faithful number" is a non-prime number that is one less or one more than some prime number but not both. For example, for num...

5 meses ago

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Easy Sequences 5: Project Euler Problem 1 - Again!
We are all familiar with Project Euler Problem 1. This time let's try it on bigger multiples and larger range. Find the sum of ...

5 meses ago

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Easy Sequences 6: Coefficient sums of derivatives
Consider the polynomial function and its first-order derivative . The sums of the coefficients of P and P', are and , respecti...

5 meses ago

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Easy Sequences 4: Eliminate the Days of Confusion
If a date is written in purely numeric format some dates can be confusing, if we don't know the date format used. For example, "...

6 meses ago

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Easy Sequences 3: Prime 44-number Squares
The positive integers 62 and 238 are related. Their squares (3844 and 56,644) both end in '44'. In fact, 62 and 238 are the 3rd ...

6 meses ago

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Easy Sequences 2: Trigonometric function with integral input and output
The function 'F', defined as: , will always return an integer if the input is a natural number (in radian...

6 meses ago

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Easy Sequences 1: Find the index of an element
The nth element of a series A is defined by: . Obviously, the first element A(1) = 1. Given the nth element 'A(n)', find the val...

6 meses ago

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Toeplitize a matrix
Similar to <http://www.mathworks.com/matlabcentral/cody/problems/3094-hankelize-a-matrix Problem 3094. Hankelize a matrix>, now ...

6 meses ago

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Write a function man that takes a row vector v and returns a matrix H as follows..
Write a function called man that takes a row vector v as an input and returns a matrix H whose first column consist of the eleme...

6 meses ago

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Hankelize a matrix
Similar to <http://www.mathworks.com/matlabcentral/cody/problems/42501-toeplitize-a-matrix Problem 42501. Toeplitize a matrix>, ...

6 meses ago

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Matrix of Multiplication Facts
This is James's daughter again, sneaking into his Cody account. Thanks to your help in my math class last year, I did great! B...

6 meses ago

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Go to the head of the class!
You're given a matrix and a single number. If that number is in the matrix, reorder the matrix so that number is in the first r...

6 meses ago

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Must be in the front row...
You are given a matrix followed by a single number. Your object is to write a script that will shift the matrix around so that ...

6 meses ago

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Magnet and Iron
(Inspired from <http://www.mathworks.com/matlabcentral/cody/problems/112 Problem 112: Remove the air bubbles>) Iron (atomic n...

6 meses ago

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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 ...

6 meses ago

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Matrix multiplication across rows
Given matrix m, return matrix n such that, rows of n are result of multiplication of the rows of the input matrix Example ...

6 meses ago

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A matrix of extroverts
Now that the introverts have had their script, the extroverts spoke up (naturally!) and demanded one as well. You will be given...

6 meses ago

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Convert matrix to 3D array of triangular matrices
Given a 2D numeric array x in which each column represents the vectorized form of an upper triangular matrix, return a 3D array ...

6 meses ago

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Too Many Zeros, Dump Them!
Sometimes when I create a matrix, I use this syntax: a = zeros(1000,1000); But when the function ends, I find that I don'...

6 meses ago

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Enlarge array
Given an m-by-n numeric array (A) and a 1-by-2 vector (sz) indicating the dimensions [p q] to enlarge each element, return an (m...

6 meses ago

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Remove entire row and column in the matrix containing the input values
Remove the entire row and column from the matrix containing specific values. The specified value can be a scalar or a vector. Fo...

6 meses ago

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frame of the matrix
Given the matrix M, return M without the external frame.

6 meses ago

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subtract central cross
Given an n-by-n square matrix, where n is an odd number, return the matrix without the central row and the central column.

6 meses ago

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MatCAT - Reconstruct X from Its X-rays
Consider a matrix x x = [ 1 2 0 0 5 0 3 0 8 ] If we sum x along the rows we get row_sums = [3 5 11] ...

6 meses ago

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Given a matrix, swap the 2nd & 3rd columns
If a = [1 2 3 4; 1 2 3 4; 1 2 3 4; 1 2 3 4]; then the result is ans = 1 3 2 4 1 3 2...

6 meses ago

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matrix zigzag
Unfold a 2-D matrix to a 1-D array in zig-zag order, e.g., for matrix [ 1 2 3 ; 4 5 6 ; 7 8 9 ] the resulting 1-...

6 meses ago

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Determine the number of odd integers in a vector
Determine the number of unique odd integers in a vector. Examples: Input x = [2 5 8 3 7 1]; Output y = 4; Inp...

6 meses ago

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Reference Index Number
Given a reference set R of elements (each unique but identical in type), and a list V of elements drawn from the set R, possibly...

6 meses ago