Converting decimal to binary, help!!

SB
2012 11 2
1 个回答
3 次查看（30 天）

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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

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SB
SB 2012-11-2
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
Image Analyst 2012-11-2
In the past, has changing your name ever worked to help you to understand how to write code?

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回答（1 个）

John Petersen
John Petersen 2012-11-2

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SB
SB 2012-11-2
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
Jan 2012-11-2
@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
SB 2012-11-2
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
John Petersen 2012-11-2
编辑：John Petersen 2012-11-2
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
John Petersen 2012-11-2
Also, the last line
bin=bin1+bin2
will fail because these are strings. To concatenate strings, simply do
bin = [bin1, bin2];

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SB
SB
2012-11-2

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