Computational Neuro: MATLab Basics

This semester, I took on Computational Neuroscience with lab. It’s been a difficult class (I always say that) by it’s been amazing to learn how to use MATLab in neural coding sequences in my Last semester of college. Here’s some of my notes on the basics of neural coding within MATLab!

Before we get started…

Here is the basic syntax of MATLab. MATLab works in array that store information about variables. These arrays can be scalars, vectors, or matrices. The information that they hold can have various values, from logical numbers, to functions, to imaginary numbers and place holders.

Basic syntax

Example	Description
`x = 9`	Create variables with the equal sign (`=`). The left-side (`x`) is the variable name containing the value on the right-side (`pi`).
`y = sin(1)`	You can provide inputs to a function using parentheses.

Desktop management

Function	Example	Description
`save`	`save data.mat`	Save your current workspace to a MAT-file.
`load`	`load data.mat`	Load the variables in a MAT-file to the Workspace.
`clear`	`clear`	Clear all variables from the Workspace.
`clc`	`clc`	Clear all text from the Command Window.
`format`	`format long`	Change how numeric output is displayed.

Array types

Example	Description
`4`	scalar
`[3 5]`	row vector
`[1;3]`	column vector
`[3 4 5;6 7 8]`	matrix

Evenly-spaced vectors

Example	Description
`1:4`	Create a vector from `1` to `4`, spaced by `1`, using the colon (`:`) operator.
`1:0.5:4`	Create a vector from `1` to `4`, spaced by `0.5`.
`linspace(1,10,5)`	Create a vector with `5` elements. The values are evenly spaced from `1` to `10`.

Creating matrices

Example	Description
`rand(2)`	Create a square matrix with `2` rows and `2` columns.
`zeros(2,3)`	Create a rectangular matrix with `2` rows and `3` columns.

Indexing

Example	Description
`A(end,2)`	Access the element in the second column of the last row.
`A(2,:)`	Access the entire second row
`A(1:3,:)`	Access all columns of the first three rows.
`A(2) = 11`	Change the value of the second element an array to `11`.

Array operations

Example	Description
[1 1; 1 1]*[2 2;2 2] ans = 4 4 4 4	Perform matrix multiplication.
[1 1; 1 1].*[2 2;2 2] ans = 2 2 2 2	Perform element-wise multiplication.

Multiple outputs

Example	Description
`[xrow,xcol] = size(x)`	Save the number of rows and columns in `x` to two different variables.
`[xMax,idx] = max(x)`	Calculate the maximum value of `x` and its corresponding index value.

Documentation

Example	Description
`doc randi`	Open the documentation page for the `randi` function.

Plotting

Example	Description
`plot(x,y,"ro-","LineWidth",5)`	Plot a red (`r`) dashed (`--`) line with a circle (`o`) marker, with a heavy line width.
`hold on`	Add the next line to existing plot.
`hold off`	Create a new axes for the next plotted line.
`title("My Title")`	Add a label to a plot.

Using tables

Example	Description
`data.HeightYards`	Extract the variable `HeightYards` from the table `data`.
`data.HeightMeters = data.HeightYards*0.9144`	Derive a table variable from existing data.

Logicals

Example	Description
`[5 10 15] > 12`	Compare a vector to the value `12`.
`v1(v1 > 6)`	Extract all elements in `v1` that are greater than `6`.
`x(x==999) = 1`	Replace all values in `x` that are equal to `999` with the value `1`.

Programming

Example Description

Example	Description
if x > 0.5 y = 3 else y = 4 end	If `x` is greater than `0.5`, set the value of `y` to `3`. Otherwise, set the value of `y` to `4`.
for c = 1:3 disp(c) end	The loop counter (`c`) progresses through the values `1:3` (`1`, `2`, and `3`).The loop body displays each value of `c`.

if x > 0.5
    y = 3
else
    y = 4
end

If x is greater than 0.5, set the value of y to 3.

Otherwise, set the value of y to 4.

for c = 1:3
    disp(c)
end

The loop counter (c) progresses through the
values 1:3 (1, 2, and 3).The loop body displays each value of c.

Nico Addae Miss Minds