if-statements for reassigning values

Given: Write a script that creates a random integer N, which is in the range [-100,100]. If that number is in the range [-20,20], reassign N to be the current value of N multiplied by 2. If the number is greater than 20, reassign N to be the square root of the current value. Otherwise, reassign N to be the current value divided by 4.

Find: Use an if-statement to complete this.

Issue: I'm getting errors stating I don't know how to use '='. To me, my solution makes sense. But I have trouble with syntax in MATLAB.

My Solution:

N=randi([-100,100]);
if N=[-20,20]
    N=N*2
else if N>20
        N=sqrt(N)
else 
    N=N/4
end

Answer 1

[Voss]

Use

if N >= -20 && N <= 20

And remove the space in "else if".

[Spaceman]

Eureka! Of course. Now I get it. I want to accept both yours and Mr. Lords answer, but unfortunately I can only pick one.

[Voss]

Glad it makes sense!

[Spaceman]

Thank you so much for your help!

[Voss]

You're welcome!

[Spaceman]

You're a real one!

Answer 2

[Steven Lord]

Let's look at the exact text of the error you received.

N=randi([-100,100]);
if N=[-20,20]

Incorrect use of '=' operator. Assign a value to a variable using '=' and compare values for equality using '=='.

    N=N*2
else if N>20
        N=sqrt(N)
else 
    N=N/4
end

Using "N = [-20 20]" attempts to assign a vector with two elements to N. Assignment is not allowed in the condition part of an if statement.

Using "N == [-20 20]" (assuming N is compatibly sized) compares elements of N with elements of the vector [-20 20]. Comparison is allowed in the condition part of an if statement.

But you don't want to check if the elements in N are equal to -20 and 20. You want to check if they're in that interval. For that use the four inequality relational operators like < and >=. The and, & and or, | operators will also be of use.

[Spaceman]

Genius. This makes complete sense I forget I am generally only using logical operators with if and elseif statements. Also as Voss pointed out, I had a space in my elseif. Thank you for clearing that up.