Numeric data becomes zero after conversion from Table

Question

Rainer Rodrigues 2023-1-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1901045-numeric-data-becomes-zero-after-conversion-from-table

回答： Walter Roberson 2023-1-26

采纳的回答： Walter Roberson

I am trying to extract data collected via IMU using the readtable function like this:

%Extracting data from the LGW folder

[filename, pathname] = uigetfile('*.dat');

T1 = readtable(strcat(pathname,filename),"ReadVariableNames",true);

T1 = T1(:,1:end-2);

[filename, pathname] = uigetfile('*.dat');

T2 = readtable(strcat(pathname,filename));

T2 = T2(:,1:end-2);

[filename, pathname] = uigetfile('*.dat');

T3 = readtable(strcat(pathname,filename));

T3 = T3(:,1:end-2);

[filename, pathname] = uigetfile('*.dat');

T4 = readtable(strcat(pathname,filename));

T4 = T4(:,1:end-2);

T4(:,[51 52]) = [];

[filename, pathname] = uigetfile('*.dat');

T5 = readtable(strcat(pathname,filename));

T5 = T5(:,1:end-2);

T5(:,[51 52]) = [];

[filename, pathname] = uigetfile('*.dat');

T6 = readtable(strcat(pathname,filename));

T6 = T6(:,1:end-2);

T6(:,[51 52]) = []

However, when converting it to numeric data like this:

nums = [LGW_Pelvis{2,:}]

The data becomes zero except for the all the row under the first column.

I have tried changing the format into cell and timetable but when getting the numeric data format from these data types: they becomes zero.

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Walter Roberson 2023-1-26

在 MATLAB Online 中打开

Okay, please show us

unique(varfun(@class, data_LGW(1,61:70), 'OutputFormat', 'cell'))

Rainer Rodrigues 2023-1-26

ans = 1×1 cell array

{'double'}

This is the given output.

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Answer 1

Walter Roberson 2023-1-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1901045-numeric-data-becomes-zero-after-conversion-from-table#answer_1157270

在 MATLAB Online 中打开

I predict that you have

format short

in effect, and that what is being displayed is not really 0 but is instead something of the form

x = [0,10.^(-5:5)]
x = 1×12
1.0e+05 *

         0    0.0000    0.0000    0.0000    0.0000    0.0000    0.0000    0.0001    0.0010    0.0100    0.1000    1.0000

Notice the initial "1.0e+5 *" before the line, and notice the "0.0000" entries. The "1.0e+5 *" indicates that you need to mentally multiply all of the displayed outputs by 1.0e+5. The 0.0000 entries indicate something that is not exactly zero, but instead is smaller than 0.0001 times the value shown in the first line. Notice the exact 0 at the begining is shown without the ".0000" .

I predict that if you were to

format long g
x
x = 1×12
1.0e+00 *

                         0                     1e-05                    0.0001                     0.001                      0.01                       0.1                         1                        10                       100                      1000                     10000                    100000

then you would see the actual values.