如何从 a.csv 文件中读取带有 readtable 的确切小数位数？

Question

I want to read a.csv file containing numbers with more than 17 decimal digits by using the function readtable. I manage to perform this task but the collected data has a reduced number of decimal digits with respect to data stored into orginal.csv file.

How can I keep the same number of decimal digits as in the original file in matlab?

Here an example code that tries to read the.csv file "NEOs_asteroids.csv" attached to this question:

clear all; close all; clc;

file_name_asteroids = 'NEOs_asteroids.csv';

% Options settings 
opts = detectImportOptions(file_name_asteroids);
opts.DataLines = 2;
opts.VariableNamesLine = 1;

% Read data into a table array
Asteroids_orbit_elem = readtable(file_name_asteroids,opts);

Here the.csv file "NEOs_asteroids.csv" (I have only inserted a few lines because of the excessive number of them):

"pdes","name","epoch","a","e","i","om","w","ma"
433,Eros,2459600.5,1.458273100364966,.2227273342470533,10.82846064209305,304.2963534821116,178.8971619902451,246.9041236220357
719,Albert,2459600.5,2.63750535267235,.5469586853330971,11.57526970278196,183.8552591536149,156.2275765643465,278.1971857577304
887,Alinda,2459600.5,2.473158049128383,.5704858457447907,9.394142747629626,110.4288007693465,350.4932417946612,86.60720939790032
1036,Ganymed,2459600.5,2.665849369179047,.5331216208605787,26.6779034163866,215.5172093946143,132.4281002671606,140.6548420252212
1221,Amor,2459600.5,1.918731194899893,.4358425037702864,11.88326264445768,171.320253219285,26.64392069638918,261.0445055510584
1566,Icarus,2459600.5,1.078092896249167,.8269435773988872,22.80421609750081,87.96160578064956,31.43750761745641,.3302900481594904
1580,Betulia,2459600.5,2.197288160959855,.4871550690589618,52.07925829047207,62.2921305585828,159.5134530240992,16.62891169416756
1620,Geographos,2459600.5,1.245689288382424,.3353623815747189,13.33753650197932,337.1849253154281,276.9463790257625,300.4925456677647
1627,Ivar,2459600.5,1.863273429711433,.3967369932429542,8.451956515515922,133.1203083485335,167.8035837515731,129.0289785118674
1685,Toro,2459600.5,1.367465568905196,.435966790549019,9.382739662870495,274.2362441040706,127.2114688956593,300.0617970060148
1862,Apollo,2459600.5,1.470502475713431,.5600430467767759,6.353083928279622,35.56898244993719,286.0386669340027,60.20237527657879
1863,Antinous,2459600.5,2.25922922966352,.6059920366929147,18.39886422664638,346.4237098245764,268.0896471241496,244.0101430178307
1864,Daedalus,2459600.5,1.460979692497152,.614486601048712,22.21536436924144,6.613194566464952,325.6563726322316,196.1166696209867
1865,Cerberus,2459600.5,1.079986459127503,.4669721847798676,16.09858904525619,212.8963846822369,325.2653260753237,170.2073771841984
1866,Sisyphus,2459600.5,1.893353802479725,.5383695942642949,41.20637430558688,63.47259682927852,293.0824330786623,331.1476239661798
1915,Quetzalcoatl,2459600.5,2.543790754476287,.5706410666538692,20.40472660837776,162.9348721741076,347.8091351438147,41.39145147165023
1916,Boreas,2459600.5,2.272324177667199,.4498393843780145,12.88297395642586,340.5981620510102,335.9167764123868,352.2401366045371
1917,Cuyo,2459600.5,2.149811212264342,.5054666607934076,23.95922692432141,188.2869783183211,194.5115030152427,82.28439227062766
1943,Anteros,2459600.5,1.430366783173011,.2560374828122278,8.706034969532251,246.3110706020363,338.3801329232052,173.8814283992249

Answer 1

It is likely that you are running into a precision limitation of the floating point format used internally by MATLAB. MATLAB by default uses doubles to store pretty much all numbers. For an IEEE double you're only going to get about 15 decimal digits .

If you're not planning on performing computations on these numbers an option is to read them in as strings :

opts = detectImportOptions(filename);
opts = setvartype(opts, 'your variable', 'string');  % or 'char'
data = readtable(filename, opts);

If you want to perform computations on these numbers things are somewhat more difficult. A "built-in" option is to use the variable-precision arithmetic in the Symbolic Math Toolbox, or roll you own implementation. I'd consider if you really need the precision first before going down either of these paths for more precision.