getting very weird number from hex2dec()

Hello,

I am attempting to convert large matrices of doubles to hex. I have an S matrix [2048 x 984] full of zeros

If I do this

>> dec2hex(s1a(1,3))

ans =

0

which is what should happen. However If I do this.....

HexS1a = ones(2048,984);
for aa = 1:984
    for bb = 1:2048
    HexS1a(bb,aa) = HexS1a(bb,aa)*dec2hex(s1a(bb,aa));
    end
end

I get a matrix of "48"'s not zeros. The type is double. Can anyone explain this? It's driving me nuts!

Answer 1

[Walter Roberson]

dec2hex(sla(1,3)) is not producing a digit zero: it is producing the string '0' . The numeric code for the character '0' happens to be 48. char(48) = '0'

ones(2048,984) is a double precision datatype. When you store a character to a double precision data type, the character gets converted to its numeric code.

If you are planning to multiply hex digits then you will need something more sophisticated that the "*" operator.

Answer 2

[William]

how would I go about rigging it so I just get zero?

[Walter Roberson]

t = dec2hex(sla(1,3)) - '0';

t(t>9) = t(t>9) - 7;

However, if this is your aim, to get the numeric equivalent of each group of 4 bits, you can do that in other ways. For example,

HexPerVal = 2; %hex digits per sla entry

t2 = reshape(dec2bin(sla(:),HexPerVal*4).', 4, []).' - '0';

t3 = reshape(t2(:,1) * 8 + t2(:,2) * 4 + t2(:,3) * 2 + t2(:,4),2,[]).';

t4 = permute(reshape(t3,[HexPerVal,3,5]),[2 3 1]);

Now t4 would be an array whose first two dimensions were the same as sla's dimensions, and whose third dimension would be 1 to the number of hex digits per value (as determined by HexPerval)