Avoiding unpacking an array when altering its dimension












2












$begingroup$


I am trying to flatten a matrix from 3-dimensional to 2-dimensional one.



The original one has dimension for example {10,120,120}:



list1 = RandomReal[1, {10, 120, 120}];


I want to convert it to a new matrix with {10,120*120} dimension. I am using:



On["Packing"]  (*For checking if exist unpacked arrays *)  
Flatten[Map[Flatten, {list1}, {-3}], 1];


But this will generate unpacked array. How should I avoid this issue?










share|improve this question











$endgroup$








  • 2




    $begingroup$
    Try Flatten[list1, {{1}, {2, 3}}].
    $endgroup$
    – J. M. is computer-less
    2 hours ago










  • $begingroup$
    Thanks, it works!
    $endgroup$
    – cj9435042
    1 hour ago










  • $begingroup$
    Flatten /@ list1
    $endgroup$
    – Okkes Dulgerci
    38 mins ago
















2












$begingroup$


I am trying to flatten a matrix from 3-dimensional to 2-dimensional one.



The original one has dimension for example {10,120,120}:



list1 = RandomReal[1, {10, 120, 120}];


I want to convert it to a new matrix with {10,120*120} dimension. I am using:



On["Packing"]  (*For checking if exist unpacked arrays *)  
Flatten[Map[Flatten, {list1}, {-3}], 1];


But this will generate unpacked array. How should I avoid this issue?










share|improve this question











$endgroup$








  • 2




    $begingroup$
    Try Flatten[list1, {{1}, {2, 3}}].
    $endgroup$
    – J. M. is computer-less
    2 hours ago










  • $begingroup$
    Thanks, it works!
    $endgroup$
    – cj9435042
    1 hour ago










  • $begingroup$
    Flatten /@ list1
    $endgroup$
    – Okkes Dulgerci
    38 mins ago














2












2








2





$begingroup$


I am trying to flatten a matrix from 3-dimensional to 2-dimensional one.



The original one has dimension for example {10,120,120}:



list1 = RandomReal[1, {10, 120, 120}];


I want to convert it to a new matrix with {10,120*120} dimension. I am using:



On["Packing"]  (*For checking if exist unpacked arrays *)  
Flatten[Map[Flatten, {list1}, {-3}], 1];


But this will generate unpacked array. How should I avoid this issue?










share|improve this question











$endgroup$




I am trying to flatten a matrix from 3-dimensional to 2-dimensional one.



The original one has dimension for example {10,120,120}:



list1 = RandomReal[1, {10, 120, 120}];


I want to convert it to a new matrix with {10,120*120} dimension. I am using:



On["Packing"]  (*For checking if exist unpacked arrays *)  
Flatten[Map[Flatten, {list1}, {-3}], 1];


But this will generate unpacked array. How should I avoid this issue?







list-manipulation packed-arrays






share|improve this question















share|improve this question













share|improve this question




share|improve this question








edited 1 hour ago









m_goldberg

87.2k872197




87.2k872197










asked 2 hours ago









cj9435042cj9435042

35416




35416








  • 2




    $begingroup$
    Try Flatten[list1, {{1}, {2, 3}}].
    $endgroup$
    – J. M. is computer-less
    2 hours ago










  • $begingroup$
    Thanks, it works!
    $endgroup$
    – cj9435042
    1 hour ago










  • $begingroup$
    Flatten /@ list1
    $endgroup$
    – Okkes Dulgerci
    38 mins ago














  • 2




    $begingroup$
    Try Flatten[list1, {{1}, {2, 3}}].
    $endgroup$
    – J. M. is computer-less
    2 hours ago










  • $begingroup$
    Thanks, it works!
    $endgroup$
    – cj9435042
    1 hour ago










  • $begingroup$
    Flatten /@ list1
    $endgroup$
    – Okkes Dulgerci
    38 mins ago








2




2




$begingroup$
Try Flatten[list1, {{1}, {2, 3}}].
$endgroup$
– J. M. is computer-less
2 hours ago




$begingroup$
Try Flatten[list1, {{1}, {2, 3}}].
$endgroup$
– J. M. is computer-less
2 hours ago












$begingroup$
Thanks, it works!
$endgroup$
– cj9435042
1 hour ago




$begingroup$
Thanks, it works!
$endgroup$
– cj9435042
1 hour ago












$begingroup$
Flatten /@ list1
$endgroup$
– Okkes Dulgerci
38 mins ago




$begingroup$
Flatten /@ list1
$endgroup$
– Okkes Dulgerci
38 mins ago










1 Answer
1






active

oldest

votes


















4












$begingroup$

An alternative to using Flatten as in the comments is to use ArrayReshape. For large arrays, ArrayReshape should be significantly faster. For example:



list1 = RandomReal[1, {10, 1200, 1200}];


Comparison:



r1 = Flatten[list1, {{1}, {2, 3}}]; //RepeatedTiming
r2 = ArrayReshape[list1, {10, 1200 1200}]; //RepeatedTiming

r1 === r2



{0.120, Null}



{0.025, Null}



True







share|improve this answer









$endgroup$













  • $begingroup$
    I'm too slow..... :)
    $endgroup$
    – Michael E2
    1 hour ago











Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "387"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmathematica.stackexchange.com%2fquestions%2f192623%2favoiding-unpacking-an-array-when-altering-its-dimension%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown

























1 Answer
1






active

oldest

votes








1 Answer
1






active

oldest

votes









active

oldest

votes






active

oldest

votes









4












$begingroup$

An alternative to using Flatten as in the comments is to use ArrayReshape. For large arrays, ArrayReshape should be significantly faster. For example:



list1 = RandomReal[1, {10, 1200, 1200}];


Comparison:



r1 = Flatten[list1, {{1}, {2, 3}}]; //RepeatedTiming
r2 = ArrayReshape[list1, {10, 1200 1200}]; //RepeatedTiming

r1 === r2



{0.120, Null}



{0.025, Null}



True







share|improve this answer









$endgroup$













  • $begingroup$
    I'm too slow..... :)
    $endgroup$
    – Michael E2
    1 hour ago
















4












$begingroup$

An alternative to using Flatten as in the comments is to use ArrayReshape. For large arrays, ArrayReshape should be significantly faster. For example:



list1 = RandomReal[1, {10, 1200, 1200}];


Comparison:



r1 = Flatten[list1, {{1}, {2, 3}}]; //RepeatedTiming
r2 = ArrayReshape[list1, {10, 1200 1200}]; //RepeatedTiming

r1 === r2



{0.120, Null}



{0.025, Null}



True







share|improve this answer









$endgroup$













  • $begingroup$
    I'm too slow..... :)
    $endgroup$
    – Michael E2
    1 hour ago














4












4








4





$begingroup$

An alternative to using Flatten as in the comments is to use ArrayReshape. For large arrays, ArrayReshape should be significantly faster. For example:



list1 = RandomReal[1, {10, 1200, 1200}];


Comparison:



r1 = Flatten[list1, {{1}, {2, 3}}]; //RepeatedTiming
r2 = ArrayReshape[list1, {10, 1200 1200}]; //RepeatedTiming

r1 === r2



{0.120, Null}



{0.025, Null}



True







share|improve this answer









$endgroup$



An alternative to using Flatten as in the comments is to use ArrayReshape. For large arrays, ArrayReshape should be significantly faster. For example:



list1 = RandomReal[1, {10, 1200, 1200}];


Comparison:



r1 = Flatten[list1, {{1}, {2, 3}}]; //RepeatedTiming
r2 = ArrayReshape[list1, {10, 1200 1200}]; //RepeatedTiming

r1 === r2



{0.120, Null}



{0.025, Null}



True








share|improve this answer












share|improve this answer



share|improve this answer










answered 1 hour ago









Carl WollCarl Woll

68.9k391177




68.9k391177












  • $begingroup$
    I'm too slow..... :)
    $endgroup$
    – Michael E2
    1 hour ago


















  • $begingroup$
    I'm too slow..... :)
    $endgroup$
    – Michael E2
    1 hour ago
















$begingroup$
I'm too slow..... :)
$endgroup$
– Michael E2
1 hour ago




$begingroup$
I'm too slow..... :)
$endgroup$
– Michael E2
1 hour ago


















draft saved

draft discarded




















































Thanks for contributing an answer to Mathematica Stack Exchange!


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


Use MathJax to format equations. MathJax reference.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmathematica.stackexchange.com%2fquestions%2f192623%2favoiding-unpacking-an-array-when-altering-its-dimension%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

Knooppunt Holsloot

Altaar (religie)

Gregoriusmis