How do I write a script file that asks the user to input the total resistance for a resistor and then outputs a list of colors for the bands in order (1, 2, 3)?

A resistor has three colored bands that shows its total resistance. The total resistance = ((color of first band)*10 + (color of second band))*10^(color of the third band)

black is 0
brown is 1
red - 2
orange - 3
yellow - 4
green - 5
blue - 6
violet - 7
gray - 8
white -9

[Geoff Hayes]

Ian - is the idea that the code must determine which of the three colours can be used in the above equation that returns the total resistance that the user entered? Do all combinations have to be determined? If you want to get user input, use input to request that the user enter a total resistance.

 totalResistance = input('Please enter the total resistance: ');

Does your code now iterate over all possible combinations (504 of them?) to determine which triple produces totalResistance? What if no such triple exists?

[Haldi Mandalahi]

 totalResistance = input('Please enter the total resistance: ');

Answer 1

[Star Strider]

This takes me back to my amateur radio days (although I was used to mapping from stripes to resistance):

Colours = {'black' 'brown' 'red' 'orange' 'yellow' 'green' 'blue' 'violet' 'gray' 'white'};
Values = [0:9];

Rc = inputdlg('Stripe your resistor!  What is its resistance (Ω)? ')
Rstr = Rc{:};
for k1 = 1:length(Rstr)
    parse{k1} = Rstr(k1);
end
Mult = fix(log10(str2num(Rstr)));
Bands = parse(1:2);
Resistor = Colours([str2num(Bands{1})+1, str2num(Bands{2})+1, Mult])
fprintf(1, '\tYour resistor of %s Ohms will be striped %s, %s, %s\n\n', Rstr, char(Resistor{1}), char(Resistor{2}), char(Resistor{3}))

Example output:

Your resistor of 47000 Ohms will be striped yellow, violet, orange

[Ian Hiltner]

I just began learning Matlab. So far, all we learned is basic the if and for loops/statements, arrays, and how to input and output variables. So I don't know what any of your code means. Sorry. Is there a way to do the problem by using if statements and simple Matlab functions?

[Star Strider]

It actually doesn’t need if statements, and it uses one loop to parse the numeric input (converted to a string).

It first takes the resistance input ‘Rc’ through the inputdlg call, creates a string vector from it with ‘Rstr’ then parses it into individual numbers in the loop, creating the cell array ‘parse’. In ‘Mult’, it creates the multiplier by taking exponent of the base 10 log of the numeric value of the resistance. It then calculates the ‘Bands’ by taking the values of the first two numbers in the resistance, appending ‘Mult’ to it, creating a vector of three subscript references to the ‘Colours’ cell array. It then puts those colours together in the ‘Resistor’ cell array, and outputs it and the original value of the resistance in the fprintf statement.

It is probably possible to put all this together with a set of if statements or a switch...case block, but this is a much more efficient way to do the coding. I cannot in good conscience teach you inefficient coding techniques when efficient methods are available.

[Ian Hiltner]

Thank you for clarifying. I appreciate your help.

[Star Strider]

My pleasure.