# Rick Amos

### MathWorks

Developer at MathWorks, working on Parallel Computing Toolbox.

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**Content Feed**

Reading portions of several CSV files

You might want to take a look at tabularTextDatastore and/or tall arrays. These are geared up to do exactly this kind of thing:-...

3 years ago | 5

tallArray sorting and plot error

Instead of converting State to a character vector, I would recommend using one of the string utilities. These are all supported ...

3 years ago | 0

Pass fileDatastore explicit AWS credentials

It is currently not possible to pass explicit credentials directly into fileDatastore. Datastore retrieves the credentials in th...

3 years ago | 0

Too many .mat files when using Write Tall Table

As you've likely guessed, vertical concatenation of 1600 arrays results in at least 1600 files from tall/write. This is the case...

4 years ago | 0

| accepted

Generate a Datastore for binary data?

As of R2017b, MATLAB now allows you to write custom datastores. This will allow you to create datastores that handle large binar...

5 years ago | 2

How to check Hadoop and Matlab Integrated Properly or Not ???

To look at whether MATLAB is running on the Hadoop cluster correctly, your best bet is to look at the Hadoop/Yarn Web UI. By def...

5 years ago | 0

| accepted

How to create tall datastore from multiple data parts?

A datastore can be created from a collection of folders and so the easiest way to achieve this is to place each block of data in...

6 years ago | 0

Datastore for custom files

For files on Hadoop, the File Datastore makes a temporary copy of the file on the local drive to be read by the ReadFcn. The Rea...

7 years ago | 0

| accepted

How to solve ' All the input files must be Sequence files. Invalid file: '' '

This error message occurred because MATLAB could not find the output files generated by the Hadoop Job. For now, this error mess...

7 years ago | 1

| accepted

How to solve" The user home directory '/homes/' for the cluster either did not exist or was not writable by the HADOOP user."

The '/homes/' folder is related to the Hadoop property 'mapreduce.admin.user.home.dir'. This is used by Hadoop to set the HOME e...

7 years ago | 1

| accepted

How to make a MAT-file that can be used to create a Datastore for MapReduce?

In R2014b there is currently not a direct way of creating a MAT file datastore. However, there are several indirect ways that wi...

8 years ago | 2

| accepted

Mapreduce does not seem to use all available cores

In R2014b, there are some limitations with the minimum size of data that can be parallelized. To avoid this limitation, the inpu...

8 years ago | 0

| accepted

MCR problems with linux/hadoop

This behavior arises because Hadoop defines the 'HOME' environment variable of task processes to be '/homes' by default. MATLAB ...

8 years ago | 0

Solved

Mandelbrot Numbers

The <http://en.wikipedia.org/wiki/Mandelbrot_set Mandelbrot Set> is built around a simple iterative equation. z(1) = c z...

11 years ago

Solved

Find the longest sequence of 1's in a binary sequence.

Given a string such as s = '011110010000000100010111' find the length of the longest string of consecutive 1's. In this examp...

11 years ago

Solved

Encode Roman Numerals

Create a function taking a non-negative integer as its parameter and returning a string containing the Roman Numeral representat...

11 years ago

Solved

Clean the List of Names

Given a list of names in a cell array, remove any duplications that result from different capitalizations of the same string. So...

11 years ago

Solved

Counting in Finnish

Sort a vector of single digit whole numbers alphabetically by their name, in Finnish. See the Wikipedia page for <http://en.wik...

11 years ago

Solved

Indexed Probability Table

This question was inspired by a Stack Overflow question forwarded to me by Matt Simoneau. Given a vector x, make an indexed pro...

11 years ago

Solved

De-dupe

Remove all the redundant elements in a vector, but keep the first occurrence of each value in its original location. So if a =...

11 years ago

Solved

Renaming a field in a structure array

MATLAB has a <http://www.mathworks.com/help/techdoc/ref/setfield.html setfield> and a <http://www.mathworks.com/help/techdoc/ref...

11 years ago

Solved

Target sorting

Sort the given list of numbers |a| according to how far away each element is from the target value |t|. The result should return...

11 years ago

Solved

Function Iterator

Given a handle fh to a function which takes a scalar input and returns a scalar output and an integer n >= 1, return a handle f...

11 years ago

Solved

Make a Palindrome Number

Some numbers like 323 are palindromes. Other numbers like 124 are not. But look what happens when we add that number to a revers...

11 years ago

Solved

Duplicates

Write a function that accepts a cell array of strings and returns another cell array of strings *with only the duplicates* retai...

11 years ago

Solved

Remove all the words that end with "ain"

Given the string s1, return the string s2 with the target characters removed. For example, given s1 = 'the main event' your ...

11 years ago

Solved

Trimming Spaces

Given a string, remove all leading and trailing spaces (where space is defined as ASCII 32). Input a = ' singular value deco...

11 years ago

Solved

Reverse Run-Length Encoder

Given a "counting sequence" vector x, construct the original sequence y. A counting sequence is formed by "counting" the entrie...

11 years ago

Solved

Swap the first and last columns

Flip the outermost columns of matrix A, so that the first column becomes the last and the last column becomes the first. All oth...

11 years ago