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From: andrea182 on 30 Nov 2009 04:56 and if i want to do the opposit things what i have to do?? for example: element 99-element 98 element 98-element 97 element 97-element 96...and so on... Thanks a lot...
From: andrea182 on 30 Nov 2009 05:55 and why for example when it do 1.4962 - 1.4961 it give me this number...5,00000000001055e-05 it's wrong???
From: ImageAnalyst on 30 Nov 2009 08:06 On Nov 30, 5:55 am, "andrea182 " <nickfasull...(a)yahoo.it> wrote: > and why for example when it do > > 1.4962 - 1.4961 it give me this number...5,00000000001055e-05 > > it's wrong??? --------------------------------------------------------------------------------------------------------------------- You're probably just not displaying enough digits. Try putting the line format('long'); in there and seeing if your input numbers are really that or if they're being rounded to 4 decimals for display. Because when I tried to do it, it gave 0.0001 just like it should.
From: ImageAnalyst on 30 Nov 2009 08:10 On Nov 30, 4:56 am, "andrea182 " <nickfasull...(a)yahoo.it> wrote: > and if i want to do the opposit things what i have to do?? for example: > element 99-element 98 > element 98-element 97 > element 97-element 96...and so on... > > Thanks a lot... ---------------------------------------------------------------------------------- Simply reverse the vector: % Generate vectors of sample data. vector1 = randperm(15); vector1(1) = 1.4962; vector1(2) = 1.4961; format('long'); disp(vector1); % Display in command window. % Reverse the array to do the differencing in the order % element 99-element 98 % element 98-element 97 % element 97-element 96...and so on... vector1 = vector1(end:-1:1) % Subtract element i from element (i+1). diffVector1 = diff(vector1) % Subtract element (i+1) from element i. % Note it's the same except a minus sign was added. % This is what Andrea wants. diffVector2 = -diff(vector1)
From: Steven Lord on 30 Nov 2009 09:21
"andrea182 " <nickfasullo77(a)yahoo.it> wrote in message news:hf08a7$lsc$1(a)fred.mathworks.com... > and why for example when it do > > 1.4962 - 1.4961 it give me this number...5,00000000001055e-05 > > it's wrong??? No, it's probably not wrong. See Q6.1 in the newsgroup FAQ linked in my signature for an explanation, and welcome to the world of floating-point arithmetic. -- Steve Lord slord(a)mathworks.com comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ |