Re: help for time series basic operations

• To: mathgroup at smc.vnet.net
• Subject: [mg46057] Re: help for time series basic operations
• From: bobhanlon at aol.com (Bob Hanlon)
• Date: Tue, 3 Feb 2004 22:19:09 -0500 (EST)
• References: <bvpaq9\$scp\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Here are some of the ways:

al[n_] := Table[ToExpression["a"<>ToString[k]],{k,n}];

a = al[5];

b = Rest[a-RotateRight[a]]

{a2-a1,a3-a2,a4-a3,a5-a4}

b==Drop[RotateLeft[a]-a,-1]

True

b==Rest[a]-Drop[a,-1]

True

b==ListCorrelate[{-1,1}, a]

True

b==ListConvolve[{1,-1}, a]

True

Bob Hanlon

In article <bvpaq9\$scp\$1 at smc.vnet.net>, "paolo" <tarpanelli at libero.it> wrote:

<< i need some helps to begin to understand Mathematica

I have a time series
a:=[a_1,a_2,a_3,a_4,...a_n]
how can i do to subtract each element for the previous one?:

b:=[a_2 - a_1, a_3 - a_2, a_4 - a_3,.....,a_n - a_n-1] >><BR><BR>

```

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