We will speak about Basic commands and syntax in MATLAB to show how we can write code in it .
If you type in a valid expression and press Enter, MATLAB will immediately execute it and return the result.
>> 2+2
ans =
4
>> 4ˆ2
ans =
16
>> sin(pi/2)
ans =
1
>> 1/0
Warning: Divide by zero.
ans =
Inf
>> exp(i*pi)
ans =
-1.0000 + 0.0000i
Notice some of the special expressions here: pi for π, Inf for ∞, and i for √−1. Another is NaN, which stands for not a number. NaN is used to express an undefined value. For example,
>> Inf/Inf
ans =
NaN
You can assign values to variables.
>> x = sqrt(3)
x =
1.7321
>> 3*z
??? Undefined function or variable ’z’.
Observe that variables must have values before they can be used. When an expression returns a single result that is not assigned to a variable, this result is assigned to ans, which can then be used like any other variable.
>> atan(x)
ans =
1.0472
>> pi/ans
ans =
3
In floating-point arithmetic, you should not expect “equal” values to have a difference of exactly zero. The built-in number eps tells you the maximum error in arithmetic on your particular machine. For simple operations, the relative error should be less than this number. For instance,
>> exp(log(10)) - 10
ans =
1.7764e-15
>> ans/10
ans =
1.7764e-16
>> eps
ans =
2.2204e-16
Here are a few other demonstration statements.
>> % This is a comment.
>> x = rand(100,100) ; % ; means "don’t print out"
>> s = ’Hello world’ ; % quotes enclose a string
>> t = 1 + 2 + 3 + ...
4 + 5 + 6 % ... continues a line
t =
21
Once variables have been defined, they exist in the workspace. You can see what’s in the
workspace from the desktop or by using
>> who
Your variables are:
ans s t x
How to save work ?
If you enter save myfile, all the variables in the workspace will be saved to a file myfile.mat
in the current directory. Later you can use load myfile to recover the variables.
If you right-click in the Command History window and select “Create M-File. . . ”, you can
save all your typed commands to a text file. This can be very helpful for recreating what you have done.
Q:
Evaluate the following mathematical expressions in MATLAB
---- tanh(e)
---- log10 (2)
If you type in a valid expression and press Enter, MATLAB will immediately execute it and return the result.
>> 2+2
ans =
4
>> 4ˆ2
ans =
16
>> sin(pi/2)
ans =
1
>> 1/0
Warning: Divide by zero.
ans =
Inf
>> exp(i*pi)
ans =
-1.0000 + 0.0000i
Notice some of the special expressions here: pi for π, Inf for ∞, and i for √−1. Another is NaN, which stands for not a number. NaN is used to express an undefined value. For example,
>> Inf/Inf
ans =
NaN
You can assign values to variables.
>> x = sqrt(3)
x =
1.7321
>> 3*z
??? Undefined function or variable ’z’.
Observe that variables must have values before they can be used. When an expression returns a single result that is not assigned to a variable, this result is assigned to ans, which can then be used like any other variable.
>> atan(x)
ans =
1.0472
>> pi/ans
ans =
3
In floating-point arithmetic, you should not expect “equal” values to have a difference of exactly zero. The built-in number eps tells you the maximum error in arithmetic on your particular machine. For simple operations, the relative error should be less than this number. For instance,
>> exp(log(10)) - 10
ans =
1.7764e-15
>> ans/10
ans =
1.7764e-16
>> eps
ans =
2.2204e-16
Here are a few other demonstration statements.
>> % This is a comment.
>> x = rand(100,100) ; % ; means "don’t print out"
>> s = ’Hello world’ ; % quotes enclose a string
>> t = 1 + 2 + 3 + ...
4 + 5 + 6 % ... continues a line
t =
21
Once variables have been defined, they exist in the workspace. You can see what’s in the
workspace from the desktop or by using
>> who
Your variables are:
ans s t x
How to save work ?
If you enter save myfile, all the variables in the workspace will be saved to a file myfile.mat
in the current directory. Later you can use load myfile to recover the variables.
If you right-click in the Command History window and select “Create M-File. . . ”, you can
save all your typed commands to a text file. This can be very helpful for recreating what you have done.
Q:
Evaluate the following mathematical expressions in MATLAB
---- tanh(e)
---- log10 (2)
