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# David K

##### Last seen: 7 days ago
222 total contributions since 2015

I spend a lot of time in MATLAB, with my focus on signal processing and data analysis.

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Solved

Big numbers, repeated least significant digits
This problem builds off of <http://www.mathworks.com/matlabcentral/cody/problems/3077-big-numbers-least-significant-digits/ Prob...

28 days ago

Solved

Big numbers, least significant digits
Given two numbers, x and n, return the last d digits of the number that is calculated by x^n. In all cases, d will be the number...

28 days ago

Question

Parfor converting object to double?
I am trying to parallelize some of my code to make it run quicker and ran into a weird error that I get in 2019a but not in 2020...

1 month ago | 1 answer | 0

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Question

I have been struggling to speed up my MATLAB code which loads a number of large data files into custom class objects. My two cla...

1 month ago | 1 answer | 0

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Solved

Find the biggest empty box
You are given a matrix that contains only ones and zeros. Think of the ones as columns in an otherwise empty floor plan. You wan...

2 months ago

Solved

Solitaire Cipher
Implement the <http://en.wikipedia.org/wiki/Solitaire_(cipher) solitaire cipher>. Since this is from Wikipedia, I am capturin...

2 months ago

Solved

Given a window, how many subsets of a vector sum positive
Given a vector: [1 0 -1 3 2 -3 1] and a window of 2, A sliding window would find: 1 + 0 = 1 0 - 1 = -1 ...

3 months ago

Solved

Find a subset that divides the vector into equal halves
Given a vector x, return the indices to elements that will sum to exactly half of the sum of all elements. Example: Inpu...

3 months ago

Solved

How many trades represent all the profit?
Given a list of results from trades made: [1 3 -4 2 -1 2 3] We can add them up to see this series of trades made a profit ...

3 months ago

Solved

Flag largest magnitude swings as they occur
You have a phenomenon that produces strictly positive or negative results. delta = [1 -3 4 2 -1 6 -2 -7]; Marching thr...

3 months ago

Solved

Make a run-length companion vector
Given a vector x, return a vector r that indicates the run length of any value in x. Each element in r shows how many times the ...

3 months ago

Solved

Spot the outlier
All points except for one lie on a line. Which one is the outlier? Example: You are given a list of x-y pairs in a column ...

3 months ago

Solved

With apologies to William Blake
Coder Coder, typing fast Sitting at your desk, aghast. What immortal MATLAB script will solve this problem, nice and qu...

3 months ago

Solved

Evened up (or not)
You will be provided with an array or matrix that contains various numbers, in addition to an evening variable, e, set to 1 or 0...

3 months ago

Solved

De-primed
Write a function that will multiply every prime number in the array or matrix by two, leaving all other numbers the same, and re...

3 months ago

Solved

Find out the Gray Code for a Given Binary Number
Find out <http://en.wikipedia.org/wiki/Gray_code Gray Code> for a given binary number Example Binary input 1000 Gray ...

3 months ago

Solved

Digital Neighbourhood
Given a natural number reorder its digits to create another number, closest to the given one. Examples: * 123 gives 132, ...

3 months ago

Solved

Binary Neighbourhood
Given a natural number reorder its binary form to create another number, closest to the given one. Examples: * 1 gives 2, ...

3 months ago

Solved

Convert to Binary Coded Decimal
Convert from decimal representation to <http://en.wikipedia.org/wiki/Binary-coded_decimal Binary Code Decimal> (or BCD) represen...

3 months ago

Solved

Consecutive Equation Times (of the day)
Many times throughout the day can represent mathematical equations. In this problem, we focus on the largest consecutive run of ...

3 months ago

Solved

Equation Times (of the day)
Many times throughout the day can represent mathematical equations. In this problem, we focus on times that include the four bas...

3 months ago

Solved

Power Times (of the day)
Many times throughout the day can represent mathematical equations. In this problem, we focus on times that represent powers. Fo...

3 months ago

Solved

Bit calculation
Give me the count of numbers from 1 to n having their last two bits as 0. For example function y = ret_count(4) y = x...

3 months ago

Solved

Mysterious digits operation (easy)
What is this digit operation? 0 -> 0 1 -> 9 121 -> 9 44 -> 6 15 -> 5 1243 -> 7 ...

3 months ago

Question

Major slowdown when clearing objects in the wrong order
I've built a set of custom classes that I use for accessing and analyzing our datasets. I've run into the problem that when I ru...

4 months ago | 0 answers | 0

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Question

How to disable title of ButtonGroup
I have an app I've created using App Designer. Included is a Button Group that I would like to Enable and Disable with a checkbo...

4 months ago | 1 answer | 0

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Solved

Project Euler: Problem 9, Pythagorean numbers
A Pythagorean triplet is a set of three natural numbers, a b c, for which, a^2 + b^2 = c^2 For example, 3^2 + 4^2 =...

4 months ago

Solved

Project Euler: Problem 10, Sum of Primes
The sum of the primes below 10 is 2 + 3 + 5 + 7 = 17. Find the sum of all the primes below the input, N. Thank you <http:/...

4 months ago

Solved

Project Euler: Problem 8, Find largest product in a large string of numbers
Find the greatest product of five consecutive digits in an n-digit number. 73167176531330624919225119674426574742355349194934...

4 months ago

Solved

Project Euler: Problem 7, Nth prime
By listing the first six prime numbers: 2, 3, 5, 7, 11, and 13, we can see that the 6th prime is 13. What is the Nth prime nu...

4 months ago