Converting decimal to binary, help!!

I'm trying to write a function that converts a string containing a number from decimal to binary (this number may include decimal points or a negative sign). I know to find, say the binary form of 25, I would simply find the remainder of 25/2, 12/2, 6/2, 3/2 and 1/2, and take those numbers and reverse them. I'm not sure how to implement this in code though. I also know that I need to split the string at the decimal point and identify its sign, which i've done below:

    % function[bin]=myreal2bin(decstring)
if decstring(1)=='-'
    decstring = decstring(2:end);
    F = -1;
else
    F = 1;
end
Ind = strfind(decstring, '.');
L = length(decstring);
if isempty(Ind)
    Ind = L+1;
end
Num1 = decstring(1:Ind-1);
LN1 = length(Num1);
Num2 = decstring(Ind+1:end);
LN2 = length(Num1);
  end

[SB]

Nah, I'm frustrated because I can't understand how to write the code for this problem and I've spent hours and hours trying to figure it out. I'll change my name back soon.

[Image Analyst]

In the past, has changing your name ever worked to help you to understand how to write code?

Answer 1

[John Petersen]

See http://kipirvine.com/asm/workbook/floating_tut.htm for a good tutorial.

[SB]

I understand how it works, as you just take the remainders after dividing by 2 and then the concatenated remainder around, but im not totally sure how to write it.

[Jan]

@Srijohn: You cannot be sure how to write it, until you have written it. So just start to write it and ask specific questions if you get troubles.

[SB]

Here's my function, I still can't get the answer though, Please help.

    %
function[bin]=myreal2bin(decstring)
if decstring(1)=='-'
    decstring = decstring(2:end);
    F = -1;
else
    F = 1;
end
Ind = strfind(decstring, '.');
L = length(decstring);
if isempty(Ind)
    Ind = L+1;
end
Num1 = decstring(1:Ind-1);
LN1 = length(Num1);
Num2 = decstring(Ind+1:end);
LN2 = length(Num1);
i = 1;
q = floor(str2num(Num1));
r = rem(str2num(Num1), 2);
bin1(i) = num2str(r(i));
while 2 <= q
    str2num(Num1)= q;
    i = i + 1;
    q = floor(str2num(Num1)/2);
    r = rem(str2num(Num1), 2);
    bin1(i) = num2str(r);
end
bin1(i + 1) = num2str(q);
bin1 = fliplr(bin1)
i2 = 1;
q2 = floor(str2num(Num2));
r2 = rem(str2num(Num2), 2);
bin2(i) = num2str(r2(i));
while 2 <= q
    str2num(Num2)= q;
    i2 = i2 + 1;
    q2 = floor(str2num(Num2)/2);
    r2 = rem(str2num(Num2), 2);
    bin2(i2) = num2str(r2);
end
bin2(i2 + 1) = num2str(q2);
bin2 = fliplr(bin2)

bin=bin1+bin2

[John Petersen]

What are you doing with

str2num(Num1) = q;

You cannot assign a number to a function call. I think you need to assign a temp variable to it like

floatnum = str2num(Num1);

and then use this whereever you have str2num(Num1) Try that for starters.

[John Petersen]

Also, the last line

bin=bin1+bin2

will fail because these are strings. To concatenate strings, simply do

bin = [bin1, bin2];