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I need to make a fit on a small part of my data list. To do so I need to extract data setting a condition.

Example: From the list below I would like to create a new list that contains only data whose first element (my x variable) is in between -0.4096 and -0.4089

datalist = {{-0.4096, 0.15332}, {-0.40955, 0.13269}, {-0.4095, 0.175537}, {-0.40945, 0.130859},
            {-0.4094, 0.157714}, {-0.40935, 0.121826}, {-0.4093, 0.137207},
            {-0.40925, 0.135009}, {-0.4092, 0.118774}, {-0.40915, 0.126831},
            {-0.4091, 0.127441}, {-0.40905, 0.14392}, {-0.409, 0.145507},
            {-0.40895, 0.16455}, {-0.4089, 0.145141}, {-0.40885, 0.138305},
            {-0.4088, 0.141845}, {-0.40875, 0.145874}, {-0.4087, 0.125122},
            {-0.40865, 0.140747}, {-0.4086, 0.124145}, {-0.40855, 0.146362},
            {-0.4085, 0.139892}}

Take in mind that my actual data lists are much longer that the above one.

Thank you very much for your help!

Alberto

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2
  • $\begingroup$ try Select[-0.4089<=#[[1]]<=-0.4096&]@datalist $\endgroup$
    – kglr
    Commented May 28, 2020 at 8:56
  • $\begingroup$ Your Example: paragraph actually contains all the Wolfram Language symbols of the solution you are looking for: datalist // Select[First /* Between[{-0.4089, -0.4096}]]. $\endgroup$
    – Shredderroy
    Commented Feb 20 at 0:55

5 Answers 5

Reset to default
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$\begingroup$ 
datalist = {{-0.4096, 0.15332}, {-0.40955, 0.13269}, {-0.4095, 
    0.175537}, {-0.40945, 0.130859}, {-0.4094, 0.157714}, {-0.40935, 
    0.121826}, {-0.4093, 0.137207}, {-0.40925, 0.135009}, {-0.4092, 
    0.118774}, {-0.40915, 0.126831}, {-0.4091, 0.127441}, {-0.40905, 
    0.14392}, {-0.409, 0.145507}, {-0.40895, 0.16455}, {-0.4089, 
    0.145141}, {-0.40885, 0.138305}, {-0.4088, 0.141845}, {-0.40875, 
    0.145874}, {-0.4087, 0.125122}, {-0.40865, 0.140747}, {-0.4086, 
    0.124145}, {-0.40855, 0.146362}, {-0.4085, 0.139892}};

Try this:

Select[datalist, -0.496 <= #[[1]] <= 0.4089 &]

(* {{-0.4096, 0.15332}, {-0.40955, 0.13269}, {-0.4095, 
  0.175537}, {-0.40945, 0.130859}, {-0.4094, 0.157714}, {-0.40935, 
  0.121826}, {-0.4093, 0.137207}, {-0.40925, 0.135009}, {-0.4092, 
  0.118774}, {-0.40915, 0.126831}, {-0.4091, 0.127441}, {-0.40905, 
  0.14392}, {-0.409, 0.145507}, {-0.40895, 0.16455}, {-0.4089, 
  0.145141}, {-0.40885, 0.138305}, {-0.4088, 0.141845}, {-0.40875, 
  0.145874}, {-0.4087, 0.125122}, {-0.40865, 0.140747}, {-0.4086, 
  0.124145}, {-0.40855, 0.146362}, {-0.4085, 0.139892}}   *)

or this

datalist /. {x_, y_} /; x < -0.496 || x > -0.4089 -> Nothing

(* {{-0.4096, 0.15332}, {-0.40955, 0.13269}, {-0.4095, 
  0.175537}, {-0.40945, 0.130859}, {-0.4094, 0.157714}, {-0.40935, 
  0.121826}, {-0.4093, 0.137207}, {-0.40925, 0.135009}, {-0.4092, 
  0.118774}, {-0.40915, 0.126831}, {-0.4091, 0.127441}, {-0.40905, 
  0.14392}, {-0.409, 0.145507}, {-0.40895, 0.16455}, {-0.4089, 
  0.145141}} *)

Have fun!

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1
  • $\begingroup$ Thanks!!! Both work exactly as I wanted $\endgroup$
    – alpor
    Commented May 28, 2020 at 9:09
2
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Another possibility using Pick:

Pick[datalist,Unitize[Clip[datalist[[All,1]], {-0.4096, -0.4089},{0,0}]],1]

{{-0.4096, 0.15332}, {-0.40955, 0.13269}, {-0.4095, 0.175537}, {-0.40945, 0.130859}, {-0.4094, 0.157714}, {-0.40935, 0.121826}, {-0.4093, 0.137207}, {-0.40925, 0.135009}, {-0.4092, 0.118774}, {-0.40915, 0.126831}, {-0.4091, 0.127441}, {-0.40905, 0.14392}, {-0.409, 0.145507}, {-0.40895, 0.16455}, {-0.4089, 0.145141}}

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$\begingroup$ 
list = {{99., 4.}, {-99., 5.}, {-0.4096, 0.15332}, {-0.40955, 0.13269}};

Using SequenceSplit (new in 11.3)

First @ SequenceSplit[list, {{a_, _} /; ! Between[a, {-0.496, 0.4089}]}]

{{-0.4096, 0.15332}, {-0.40955, 0.13269}}

Using Cases

Cases[ a: {b_, _} /; Between[b, {-0.496, 0.4089}] :> a] @ list

{{-0.4096, 0.15332}, {-0.40955, 0.13269}}

SequenceSplit is currently (V 13.3) slow with long lists.

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$\begingroup$

Using Interval functionality:

Clear["Global`"];
datalist = {{-0.4096, 0.15332}, {-0.40955, 0.13269}, {-0.4095, 
    0.175537}, {-0.40945, 0.130859}, {-0.4094, 0.157714}, {-0.40935, 
    0.121826}, {-0.4093, 0.137207}, {-0.40925, 0.135009}, {-0.4092, 
    0.118774}, {-0.40915, 0.126831}, {-0.4091, 0.127441}, {-0.40905, 
    0.14392}, {-0.409, 0.145507}, {-0.40895, 0.16455}, {-0.4089, 
    0.145141}, {-0.40885, 0.138305}, {-0.4088, 0.141845}, {-0.40875, 
    0.145874}, {-0.4087, 0.125122}, {-0.40865, 0.140747}, {-0.4086, 
    0.124145}, {-0.40855, 0.146362}, {-0.4085, 0.139892}};

int = Interval[{-0.4089, -0.4096}];

Pick[datalist, IntervalMemberQ[int, First@#] & /@ datalist]

Select[IntervalMemberQ[int, First@#] &][datalist]

Result:

{{-0.4096, 0.15332}, {-0.40955, 0.13269}, {-0.4095, 0.175537}, {-0.40945, 0.130859}, {-0.4094, 0.157714}, {-0.40935, 0.121826}, {-0.4093, 0.137207}, {-0.40925, 0.135009}, {-0.4092, 0.118774}, {-0.40915, 0.126831}, {-0.4091, 0.127441}, {-0.40905, 0.14392}, {-0.409, 0.145507}, {-0.40895, 0.16455}, {-0.4089, 0.145141}}

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$\begingroup$ 
list = {{99., 4.}, {-99., 5.}, {-0.4096, 0.15332}, {-0.40955, 0.13269}};

Grabbing the @eldo's list and using DeleteCases:

DeleteCases[list, {a_, _} /; ! Between[a, {-0.496, 0.4089}]]

(*{{-0.4096, 0.15332}, {-0.40955, 0.13269}}*)

Or using SequenceCases:

SequenceCases[list, {s : {a_, _} /; Between[a, {-0.496, 0.4089}]} :> s]

(*{{-0.4096, 0.15332}, {-0.40955, 0.13269}}*)

Or using Pick and IntervalIntersection:

int = Interval[{-0.496, 0.4089}];

Pick[#, IntervalIntersection[int, Interval @@ #] =!= Interval[] & /@ #] &@list

(*{{-0.4096, 0.15332}, {-0.40955, 0.13269}}*)
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