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I have a list, which consists of several nested lists, and I want to extract first elements in each of this nested list and put as one single list. how to do this? 

   {{{b->4.72971}},{{b->4.76615}},{{b->1.91842},{b->4.80339}},{{b->1.93338},{b->4.84177}},{{b->1.94861},{b->4.88068}},{{b->1.96412},{b->4.92126}},{{b->1.97992},{b->4.96216}},{{b->1.99601}},{{b->2.01241}},{{b->2.02913}},{{b->2.04617}},{{b->2.06355}},{{b->2.08127}},{{b->2.09935}},{{b->2.1178}},{{b->2.13663}},{{b->2.15585}},{{b->2.17548}},{{b->2.19553}},{{b->2.21601}},{{b->2.23694}},{{b->2.25834}},{{b->2.28021}},{{b->2.30259}},{{b->2.32548}},{{b->2.34891}},{{b->2.37289}},{{b->2.39745}},{{b->2.4226}},{{b->2.44837}},{{b->2.47479}},{{b->2.50188}},{{b->2.52967}},{{b->2.55817}},{{b->2.58743}},{{b->2.61748}},{{b->2.64833}},{{b->2.68004}},{{b->2.71264}},{{b->2.74615}},{{b->2.78063}},{{b->2.8161}},{{b->2.85263}},{{b->2.89024}},{{b->2.92899}},{{b->2.96893}},{{b->3.0101}},{{b->3.05257}},{{b->3.09638}},{{b->3.14159}},{{b->3.18826}},{{b->3.23645}},{{b->3.28622}},{{b->3.33762}},{{b->3.39071}},{{b->3.44554}},{{b->3.50216}},{{b->3.5606}},{{b->3.62089}},{{b->3.68304}},{{b->3.74702}},{{b->3.81279}},{{b->3.88026}},{{b->3.94925}},{{b->4.01955}},{{b->4.09082}},{{b->4.16259}},{{b->4.23424}},{{b->4.30495}},{{b->4.3737}},{{b->4.43922}},{{b->4.50009}},{{b->4.55476}},{{b->4.6017}},{{b->4.63965}},{{b->4.66773}},{{b->4.68562}},{{b->4.69355}},{{b->4.69221}},{{b->4.68259}},{{b->4.66581}},{{b->4.64302}},{{b->4.61527}},{{b->4.58351}},{{b->4.54857}},{{b->4.51112}},{{b->4.47174}},{{b->4.43093}},{{b->4.38908}},{{b->4.34653}},{{b->4.30356}},{{b->4.2604}},{{b->4.21725}},{{b->4.17428}},{{b->4.13163}},{{b->4.08941}},{{b->4.04772}},{{b->4.00664}},{{b->3.96625}},{{b->3.9266}}}
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    $\begingroup$ Maybe something like list[[All, 1]], list[[All, All, 1]], or list[[All, All, All, 1]] does what you want. I cannot tell because you did not give any example for desired output... $\endgroup$
    – Henrik Schumacher
    Commented Jan 30, 2019 at 16:01
  • $\begingroup$ If u look at the third root it has value 1.91842 and 4.80339 , I want to read only 1.91842 $\endgroup$
    – acoustics
    Commented Jan 30, 2019 at 16:12

1 Answer 1

Reset to default
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Is this ok?

list = {{{b -> 4.72971}}, {{b -> 4.76615}}, {{b -> 1.91842}, {b -> 
      4.80339}}, {{b -> 1.93338}, {b -> 4.84177}}, {{b -> 
      1.94861}, {b -> 4.88068}}, {{b -> 1.96412}, {b -> 
      4.92126}}, {{b -> 1.97992}, {b -> 4.96216}}, {{b -> 
      1.99601}}, {{b -> 2.01241}}, {{b -> 2.02913}}, {{b -> 
      2.04617}}, {{b -> 2.06355}}, {{b -> 2.08127}}, {{b -> 
      2.09935}}, {{b -> 2.1178}}, {{b -> 2.13663}}, {{b -> 
      2.15585}}, {{b -> 2.17548}}, {{b -> 2.19553}}, {{b -> 
      2.21601}}, {{b -> 2.23694}}, {{b -> 2.25834}}, {{b -> 
      2.28021}}, {{b -> 2.30259}}, {{b -> 2.32548}}, {{b -> 
      2.34891}}, {{b -> 2.37289}}, {{b -> 2.39745}}, {{b -> 
      2.4226}}, {{b -> 2.44837}}, {{b -> 2.47479}}, {{b -> 
      2.50188}}, {{b -> 2.52967}}, {{b -> 2.55817}}, {{b -> 
      2.58743}}, {{b -> 2.61748}}, {{b -> 2.64833}}, {{b -> 
      2.68004}}, {{b -> 2.71264}}, {{b -> 2.74615}}, {{b -> 
      2.78063}}, {{b -> 2.8161}}, {{b -> 2.85263}}, {{b -> 
      2.89024}}, {{b -> 2.92899}}, {{b -> 2.96893}}, {{b -> 
      3.0101}}, {{b -> 3.05257}}, {{b -> 3.09638}}, {{b -> 
      3.14159}}, {{b -> 3.18826}}, {{b -> 3.23645}}, {{b -> 
      3.28622}}, {{b -> 3.33762}}, {{b -> 3.39071}}, {{b -> 
      3.44554}}, {{b -> 3.50216}}, {{b -> 3.5606}}, {{b -> 
      3.62089}}, {{b -> 3.68304}}, {{b -> 3.74702}}, {{b -> 
      3.81279}}, {{b -> 3.88026}}, {{b -> 3.94925}}, {{b -> 
      4.01955}}, {{b -> 4.09082}}, {{b -> 4.16259}}, {{b -> 
      4.23424}}, {{b -> 4.30495}}, {{b -> 4.3737}}, {{b -> 
      4.43922}}, {{b -> 4.50009}}, {{b -> 4.55476}}, {{b -> 
      4.6017}}, {{b -> 4.63965}}, {{b -> 4.66773}}, {{b -> 
      4.68562}}, {{b -> 4.69355}}, {{b -> 4.69221}}, {{b -> 
      4.68259}}, {{b -> 4.66581}}, {{b -> 4.64302}}, {{b -> 
      4.61527}}, {{b -> 4.58351}}, {{b -> 4.54857}}, {{b -> 
      4.51112}}, {{b -> 4.47174}}, {{b -> 4.43093}}, {{b -> 
      4.38908}}, {{b -> 4.34653}}, {{b -> 4.30356}}, {{b -> 
      4.2604}}, {{b -> 4.21725}}, {{b -> 4.17428}}, {{b -> 
      4.13163}}, {{b -> 4.08941}}, {{b -> 4.04772}}, {{b -> 
      4.00664}}, {{b -> 3.96625}}, {{b -> 3.9266}}};

Cases[First /@ list, {x_} -> x]//TeXForm

$\small{\{b\to 4.72971,b\to 4.76615,b\to 1.91842,b\to 1.93338,b\to 1.94861,b\to 1.96412,b\to 1.97992,b\to 1.99601,b\to 2.01241,b\to 2.02913,b\to 2.04617,b\to 2.06355,b\to 2.08127,b\to 2.09935,b\to 2.1178,b\to 2.13663,b\to 2.15585,b\to 2.17548,b\to 2.19553,b\to 2.21601,b\to 2.23694,b\to 2.25834,b\to 2.28021,b\to 2.30259,b\to 2.32548,b\to 2.34891,b\to 2.37289,b\to 2.39745,b\to 2.4226,b\to 2.44837,b\to 2.47479,b\to 2.50188,b\to 2.52967,b\to 2.55817,b\to 2.58743,b\to 2.61748,b\to 2.64833,b\to 2.68004,b\to 2.71264,b\to 2.74615,b\to 2.78063,b\to 2.8161,b\to 2.85263,b\to 2.89024,b\to 2.92899,b\to 2.96893,b\to 3.0101,b\to 3.05257,b\to 3.09638,b\to 3.14159,b\to 3.18826,b\to 3.23645,b\to 3.28622,b\to 3.33762,b\to 3.39071,b\to 3.44554,b\to 3.50216,b\to 3.5606,b\to 3.62089,b\to 3.68304,b\to 3.74702,b\to 3.81279,b\to 3.88026,b\to 3.94925,b\to 4.01955,b\to 4.09082,b\to 4.16259,b\to 4.23424,b\to 4.30495,b\to 4.3737,b\to 4.43922,b\to 4.50009,b\to 4.55476,b\to 4.6017,b\to 4.63965,b\to 4.66773,b\to 4.68562,b\to 4.69355,b\to 4.69221,b\to 4.68259,b\to 4.66581,b\to 4.64302,b\to 4.61527,b\to 4.58351,b\to 4.54857,b\to 4.51112,b\to 4.47174,b\to 4.43093,b\to 4.38908,b\to 4.34653,b\to 4.30356,b\to 4.2604,b\to 4.21725,b\to 4.17428,b\to 4.13163,b\to 4.08941,b\to 4.04772,b\to 4.00664,b\to 3.96625,b\to 3.9266\}}$

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  • $\begingroup$ The piece of code that you suggested is not giving me right result $\endgroup$
    – acoustics
    Commented Jan 30, 2019 at 16:28
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    $\begingroup$ @acoustics First /@ list ? $\endgroup$
    – Jerry
    Commented Jan 30, 2019 at 16:31
  • $\begingroup$ its working, thanks. If I put Second instead of first will it read the second element? $\endgroup$
    – acoustics
    Commented Jan 30, 2019 at 16:36
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    $\begingroup$ @acoustics you're welcome :) try Cases[Last /@ list, {x_} -> x] $\endgroup$
    – Jerry
    Commented Jan 30, 2019 at 16:38
  • $\begingroup$ Got it , I have been using mathematica from past 8 months, still lot of things to learn. Thanks alot @jerry $\endgroup$
    – acoustics
    Commented Jan 30, 2019 at 16:42

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