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matlabdatatableconditional-statementsdata-filtering

How to filter a table in matlab according to a condition on the elements of one or more columns?

I read a table from a .csv file, it contains 9 columns (the first two contain strings and the others numbers in double precision) and many rows (28056 to be precise) using matlab function readtable and I stored that table in a variable of type table.

Now I would like to filter the data of all columns by imposing, for example, that the values in the column named "a" are between 0.9 and 1.1 and, at the same time, the values in the column named "e" are less than or equal to 0.3. Then I would like to obtain a new smaller table according to the above conditions containing filtered data of all columns . How can I do this?

I make an example to explain better. Let us assume that I have the first 10 rows: enter image description here They are asteroids data, so let us assume that I want to filter them by imposing a <=2, so I would like to obtain a new table where I have all columns but only the rows that satisfy my condition, i.e. a table with rows 1, 5, 6, 8, 9, 10.

Here my code:

clear all; close all; clc;

file_path = 'D:\OneDrive\MSc_Thesis\Projects\NEOs_orbits\InputFiles\';
file_name_asteroids = 'NEOs_asteroids.csv';

opts = delimitedTextImportOptions("NumVariables", 9);

% Specify range and delimiter
opts.DataLines = [2, Inf];
opts.Delimiter = ",";

% Specify column names and types
opts.VariableNames = ["pdes", "name", "epoch", "a", "e", "i", "om", "w", "ma"];
opts.VariableTypes = ["string", "string", "double", "double", "double",...
                      "double", "double", "double", "double"];

% Specify file level properties
opts.ExtraColumnsRule = "ignore";
opts.EmptyLineRule = "read";

% Specify variable properties
opts = setvaropts(opts, ["pdes", "name"], "WhitespaceRule", "preserve");
opts = setvaropts(opts, ["pdes", "name"], "EmptyFieldRule", "auto");

% Import the data
Asteroids_data = readtable([file_path,file_name_asteroids],opts);

To see the input file NEOs_asteroids.csv you can look at this link, where I have made another question: NEOs_asteroids.csv

Solution

  • You want

    new_table=Asteroids_data(Asteroids_data.a>0.9 & Asteroids_data.a<1.1 & Asteroids_data.e<0.3,:)

    which happens to be empty for the toy data. So just for the illustration of the method,

    new_table=Asteroids_data(Asteroids_data.a>2 & Asteroids_data.e<0.5,:)

new_table =

  2×9 table

 pdes       name         epoch         a          e         i         om        w         ma  
______    _________    __________    ______    _______    ______    ______    ______    ______

"1580"    "Betulia"    2.4596e+06    2.1973    0.48716    52.079    62.292    159.51    16.629
"1916"    "Boreas"     2.4596e+06    2.2723    0.44984    12.883     340.6    335.92    352.24