Help with storing data in a 4-D double matrix

4 次查看（过去 30 天）
Jake
Jake 2022-12-20
编辑： Jake 2022-12-21
I have a data set in the form of 8 columns. I have attached a dummy xlsx file to show the data structure.
As it can be seen, the data set includes [time, frequency, idx, node number, V1, V2, V3, V4]. I'm trying to sort and store these in a way such that I can access V3 values of a particular frequency and of a particular time. Purpose is to be able to access V3 values of a given time/frequency.
What I thought of the structure was something like this.
Re_vx = zeros(length(node_no), 2, length(time), length(frequency));
So I get a matrix in the form of (node_no, V3, time_set, freq_set).
How can I go about this? TIA!

请先登录，再回答此问题。

回答（1 个）

Voss
Voss 2022-12-20
Ran in:
How about storing that data set as a table:
t = readtable('new1.xlsx');
t = renamevars(t,t.Properties.VariableNames, ...
{'time','frequency','idx','node_no','V1','V2','V3','V4'})
t = 144×8 table
time frequency idx node_no V1 V2 V3 V4 ______ _________ ___ _______ _________ ________ _________ ________ 1.0472 0.1 1 1 0.2377 0.26627 0.75846 0.31877 1.0472 0.1 1 2 0.60871 0.54889 0.64385 0.088389 1.0472 0.1 1 3 0.82648 0.45033 0.38874 0.16956 1.0472 0.1 1 4 0.29342 0.23107 0.64533 0.44209 1.0472 0.1 1 5 0.26534 0.34716 0.0031364 0.681 1.0472 0.1 1 6 0.75924 0.93866 0.36407 0.27537 1.0472 0.1 1 7 0.0079028 0.33617 0.036416 0.19378 1.0472 0.1 1 8 0.46993 0.47571 0.86852 0.35832 1.0472 0.1 1 9 0.44592 0.90444 0.2673 0.30641 1.0472 0.1 1 10 0.84343 0.07228 0.19927 0.94522 1.0472 0.1 1 11 0.44459 0.078301 0.37323 0.12497 1.0472 0.1 1 12 0.94596 0.50363 0.71822 0.21068 1.0472 0.2 1 1 0.58522 0.48479 0.26291 0.72812 1.0472 0.2 1 2 0.83658 0.77427 0.60219 0.23663 1.0472 0.2 1 3 0.44332 0.1263 0.62431 0.057136 1.0472 0.2 1 4 0.11618 0.84017 0.84411 0.1615
And using logical indexing to get the values at a particular time and frequency:
my_time = t.time(15)
my_time = 1.0472
my_freq = t.frequency(15)
my_freq = 0.2000
result = t(t.time == my_time & t.frequency == my_freq,:)
result = 12×8 table
time frequency idx node_no V1 V2 V3 V4 ______ _________ ___ _______ ________ ________ _______ ________ 1.0472 0.2 1 1 0.58522 0.48479 0.26291 0.72812 1.0472 0.2 1 2 0.83658 0.77427 0.60219 0.23663 1.0472 0.2 1 3 0.44332 0.1263 0.62431 0.057136 1.0472 0.2 1 4 0.11618 0.84017 0.84411 0.1615 1.0472 0.2 1 5 0.1831 0.86732 0.65839 0.53164 1.0472 0.2 1 6 0.090321 0.091064 0.64369 0.63566 1.0472 0.2 1 7 0.24416 0.29224 0.88131 0.76682 1.0472 0.2 1 8 0.54519 0.64255 0.87907 0.47458 1.0472 0.2 1 9 0.10051 0.85658 0.65277 0.45944 1.0472 0.2 1 10 0.87678 0.076611 0.94155 0.34647 1.0472 0.2 1 11 0.59088 0.54855 0.5428 0.99147 1.0472 0.2 1 12 0.31276 0.83399 0.76469 0.8957
result.V3
ans = 12×1
0.2629 0.6022 0.6243 0.8441 0.6584 0.6437 0.8813 0.8791 0.6528 0.9416
  1 个评论
Jake
Jake 2022-12-21
编辑：Jake 2022-12-21
Thank you for the response, Voss. This works when I know the specific time or a frequency that I need the V3 values of. But I wanted to get these sorted in a way that I can access them rather easily. For example, say I want to access the V3 values of frequency f1, f2, f3 but within the time t1. If I had the desired matrix (following the dummy image I attached above), those would be val(:,:,1,1), val(:,:,2,1), val(:,:,3,1).
Also, my dataset is pretty large too :( Anyway, thank you so much for the response.
EDIT:
I realized my comment and the question I posted have some contradicting points. What I wanted is to store the values in a matrix in the form of (node_no, V3, time_set, freq_set). So, if I want to get all the V3 values of the 1st time period I can access it simply by Re_vx(:,:,1,:), or at least that's what I imagined. There should be more efficient or better ways to achieve this, and I appreciate any suggestion! :)

请先登录，再进行评论。

类别

在 Help Center 和 File Exchange 中查找有关 Matrix Indexing 的更多信息

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by