Help with a basic MATLAB question

Hey, i'm learning how to use MATLAB and I was confused on what was meant by the question. Can someone explain how I can decompose the number using rem please??

[Rik]

The task is to turn the number into a vector of its decimal components. So for 864736 you need to find a way to turn that into a vector [8 6 4 7 3 6]. Your teacher wants you to use the rem function to find those values.

You should read the documentation (type doc rem in the command window).

Since the ID has a relatively small length I would propose a different method: turn it into a char array (see sprintf) and then cast it back to a double.

[Jacob]

Thanks. So I need to work with the one that shows the example

a = 1:5;

b = 3;

r = rem(a,b) ?

How do I apply this to my number?

[Rik]

Please don't delete your question text. It is extremely rude to get free help first and then remove the potential for any future reader to benefit as well.

[Rena Berman]

(Answers Dev) Restored edit

Answer 1

[Guillaume]

Given a positive integer, e.g. x = 749623, you're supposed to decompose it into a vector of digits, for my example y = [7, 4, 9, 6, 2, 3].

• What is the remainder of 749623 / 10 ?
• What is the remainder of 74962 / 10 ?
• What is the remainder of 7496 / 10 ?
• etc.

That should be enough for you to understand what you have to do.

[Jacob]

Thanks but i'm still confused. Where does the 10 come from in the question?

[Steven Lord]

As an example, 23 is 2*10 + 3.

How would you decompose 1234 in a similar way?

[Jacob]

10*123 + 4. I don't understand how using rem gets what the question is asking for.

[Guillaume]

Where does the 10 come from in the question

Your fingers! We've been using the decimal system for a while now...

You do not decompose 1234 into 10*123 + 4. Come on, you've been taught that in primary school or even earlier. Units, Decades, Hundreds, Thousands, etc.

[Jacob]

1000 + 200 + 30 + 4. I just did what he had done with his example. I don't know how this relates to the rem function though?

[Guillaume]

As I asked, given 1234

• what is the remainder of 1234 / 10
• what is the remainder of 123 / 10
• what is the remainder of 12 / 10

and what does the rem function do?

[Rik]

Have you read the documentation for what the rem function does? It calculates the remainder.

%So for two integers a and b
rem(a,b)
%returns a value c such that
a=m*b+c
%where m is an integer m, and c<b

How do you think this relates to the decomposition here?

[Jacob]

Yeah and I don't know. Do I have to find a way to get the remainder to be ID number?

[Rik]

It is a step by step process:

• Given 1234, what is the last digit? That has the same answer as finding the remainder for 1234/10.
• Now we have a variable with the value 4, how can we convert 1234 to 123 to get it ready for the next step? Subtract the remainder and apply the division: (1234-4)/10.
• Now we have 123, what is the last digit? That has the same answer as .......
• ....

In the end you have a variable for each digit of your input number (in this case the ID).

[Jacob]

Thanks but I still don't know how to do this on Matlab. Do I start with an input thing for each of A, B, C etc. and then use the rem function?

[Walter Roberson]

six = rem(YourID, 10);
rest = (ID - six)/10;
five = rem(rest, 10);
rest = (last - five)/10;
four = rem(rest, 10);
rest = (last - four)/10;
three = rem(rest, 10);
rest = (last - three)/10;
two = rem(rest, 10);
one = (last - two)/10;

[Jacob]

Thanks Walter.

How do I let f(x) equal A*x^2 + B*x + C and then sub in f(x1)? I keep getting "undefined function or variable 'x'."

[Rik]

Read the documentation for anonymous functions.

[Jacob]

How do I restrict the range of a function on a plot?

[Rik]

Read the documentation for fplot.

[Walter Roberson]

f = @(x) one*x.^2 + two*x + three;
fplot(f, [-5 5])