Dit document is een samenvatting van het boek MATLAB: A Practical Introduction to Programming and Problem Solving, 5th Edition. Over de hoofdstukken 1 t/m 5 & 8.2. Het is gemaakt voor het vak Introduction to Matlab Programming for Behavioural Scientists. Voor de master Neuroeconomics.
Chapter 1
doc: then you find everything to look up
not use for expressions: ans, i, j
carefully look what you are doing:
>> mynum = 6 + 1
mynum = 7
>> mynum + 3
ans = 10
>> mynum
mynum =7
initializing a variable: assigning it a starting or initial value when the variable is created.
incrementing: adding to a variable
decrementing: subtracting from the value
naming a variable: max 63 characters (namelengthmax) name must start with a letter after
that it can contain letters, digits and the underscore. There is a difference between upper-
and lowercase letters. you can not use:
- who shows variables that have been defined in this Command Window (this just
shows the names of the variables)
- whos shows variables that have been defined in this Command Window (this shows
more information on the variables, similar to what is in the Workspace Window) it
shows the type(class) as well as the number of bytes used to store the value.
- clearvars clears out all variables so they no longer exist
Clearvars variablename → clears only that variable
- clear same as clearvars but also clears out functions
floating-point numbers: numbers with decimal places. “Double precision” means the number
is stored using more bits (64 bits) than “single precision” (32 bits). This allows (double):
• Higher precision (more accurate representation of decimal places).
• Larger range of numbers (can represent extremely large or small values).
int8 uses eight bits altogether to store the integer and its sign. As one bit is used for the
sign, this means that seven bits are used to store actual numbers (0s or 1s).
uint8 unsigned integer, the sign is not stored, meaning that the integer can only be positive
(or 0).
The larger the number in the type name, the larger the number that can be stored
Char is used to store either single characters (e.g., ‘x’) or character vectors, which are
sequences of characters (e.g., ‘cat’).
String is used to store strings (e.g., “hello”). Strings are enclosed in double quotes
logical is used to store true/false values
format long/short you can choose if you want long (many decimal numbers) ore short
format loose/compact when you use loose there are more witregels tussen antwoord
,ellipsis … use when you want to continue
3 + 5 ...
+ 2 ...
+1
ans =
11
>> 2 * 10^4 is the same as >>2e4
associativity: then the expression are evaluated from left to right and not by the standard
rules of * and + etc.
>> help elfun → elementary functions
>>plus(2,5)
ans =
7
→ you can use this when it is no
problem that they will be override
Random numbers in matlab are pseudorandom—they are not truly random because there
is a process that determines the next value each time.
rand used to generate uniformly distributed random real numbers; calling it generates one
random real number in the open interval (0,1).
>>rand*10 → result in open interval (0,10)
The rng function sets the initial seed. several ways in which it can be called:
>> rng('shuffle') → uses the current date and time that are returned from the built-in clock
function to set the seed
>> rng(intseed) → set the seed to the default value used when MATLAB starts up
>> rng('default')
generate a random real number in the range low to high
>> low = 3;
>> high = 5;
>> rand *(high low) + low
would generate a random real number in the open interval (3, 5)
randn is used to generate normally distributed random (around the mean) real numbers
randi(4) returns a random integer (whole number) in the range from 1 to 4. A range can also
be passed, for example, randi([3, 6]) between 3 and 6
One reason for using an integer type for a variable is to save space in memory.
,or operator has two logical expressions as operands. The result is true if either or both of the
operands are true, and false only if both operands are false.
and expression is true only if both operands are true; it is false if either or both are false.
|| and && operators in MATLAB are examples of operators that are known as short-circuit
operators. the first part, 2 < 4, is true so the entire expression is true; the second part ‘a’ ==
‘c’ would not be evaluated.
>> 2 < 4 || ‘a’ == ‘c’
xor It returns logical true if one (and only one) of the arguments is true
>> xor(3<5, ‘a’ > ‘c’)
ans =
1
>>xor(3<5, ‘a’ < ‘c’) → both true so it is false with xor
ans =
0
, Direction of Division:
• / divides the left operand by the right operand: A / B = A * B^-1.
• \ divides the right operand by the left operand: A \ B = A^-1 * B.
Matrix Applications:
• / solves for X in X * B = A.
• \ solves for X in A * X = B.
Use Cases:
• Use / when you need right division.
• Use \ to solve linear systems efficiently.
uint8 stores 2^8 or 256 integers, ranging from 0 to 255. The range of values that can be
stored in int8, however, is from -128 to +127.
>> intmin(‘int8’)
ans =
-128
>>intmax(‘int8’)
ans =
127
cast can cast a variable to a particular type, for example cast a variable to the same type
using ‘like’.
can aslo be used to convert a character to its equivalent numerical value ‘a’ to his number
this stores the double value 97 in the variable numequiv
shows that ‘a’ is the 98th character in the character encoding
char does it the other way around
use it together →
rem how many times goes it in the number and what is the result 5 goes 2 times in 13 and
remainder is 3
>> rem(13,5)
ans = 3
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