Re: For Loop problem

*To*: mathgroup at smc.vnet.net*Subject*: [mg65614] Re: [mg65595] For Loop problem*From*: "Carl K. Woll" <carlw at wolfram.com>*Date*: Tue, 11 Apr 2006 04:04:22 -0400 (EDT)*References*: <200604100631.CAA14834@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Rob wrote: > I've got to manipulate some signed 12bit integer numbers from a file and > apparently Mathematica only handles 8 and 16 bit signed numbers > (probably for a very good reason). So I bring them in as 16 bits (and > they're stored that way with a leading zero nibble) and then I have to > do the following to make sense of them. I really don't know why this > code works but it does. > > For[i = 1, i < Length[y], i++, If[y[[i]] > 2048, y[[i]] = > y[[i]] - 2048, y[[i]] = y[[i]] + 2048]]; > > So to my question: once again I had to resort to a For loop to pull this > off and I know this is a no-no. But I'm so clueless about Mathematica > that I've never come up with a more sophisticated method after a year or > so of thinking about it. Can someone help (as they usually can)? > > Thanks, Rob Assuming that your data are all integers between -2047 and 6144, you could use Mod. Here is some data: In[11]:= data=Table[Random[Integer,{-2047,6144}],{10}] Out[11]= {5745,-1569,4196,3299,5796,1621,596,-1299,1074,3547} Your method (modified with <= instead of < so that the last entry is processed): In[12]:= y=data; For[i=1,i<=Length[y],i++, If[y[[i]]>2048,y[[i]]=y[[i]]-2048,y[[i]]=y[[i]]+2048]]; y Out[14]= {3697,479,2148,1251,3748,3669,2644,749,3122,1499} Using Mod: In[15]:= Mod[2048+data,4096,1] Out[15]= {3697,479,2148,1251,3748,3669,2644,749,3122,1499} If you want 2048->0 instead of 2048->4096, use Mod[2048+data,4096] Carl Woll Wolfram Research

**References**:**For Loop problem***From:*Rob <rob@piovere.com>