Attempt to reference field of non-structure array.

Question

Fadzli 2016-11-24

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/313753-attempt-to-reference-field-of-non-structure-array

回答： Fadzli 2016-11-24

I'm trying to read and load the .mat data (originally from .csv files) as following code;

 input_data=xlsread('input_data_test.xlsx',1,'(B14:E18)'); 
[nofinput]=length(input_data(:,1)); 
start=input('press enter to start'); 
 for ww=1:nofinput;
    ii=input_data(ww,:);
    if ii(isfinite(ii(:, 1)), :); 
    run_1=ii;                     
CA=run_1(1,1)
CA_CA=CA;
x_first=run_1(1,2)
y_first=run_1(1,3)
z_first=run_1(1,4)
step_number=5
[uu]=step_number;
[cc]=26;
AAA=zeros(uu,cc);
clear uu cc
Speed=1600;
Delta_CA=0.25
Time_CA=(60/Speed)/360
Delta_t=Delta_CA*Time_CA; 
load CA0000.mat 
load CA0025.mat
load CA0050.mat
for tt=1:step_number
if CA==0  matrice_cartesian=CA0000.mat; 
elseif CA==0.25  matrice_cartesian=CA0025.mat; 
elseif CA==0.5  matrice_cartesian=CA0050.mat;
end

but there's an error message; "Attempt to reference field of non-structure array" at line "elseif CA==0.25 matrice_cartesian=CA0025.mat;" So what is the possible cause for this problem? Please help, I'm really newbie in MATLAB code. Thanks

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Walter Roberson 2016-11-24

在 MATLAB Online 中打开

Is

matrice_cartesian=CA0000.mat

intended to indicate that matrice_cartesian should be assigned the string 'CA0000.mat' or that it should be assigned what is stored in the file CA0000.mat ?

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Answer 1

Walter Roberson 2016-11-24

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/313753-attempt-to-reference-field-of-non-structure-array#answer_244524

在 MATLAB Online 中打开

My guess:

if CA==0  matrice_cartesian=CA0000; 
elseif CA==0.25  matrice_cartesian=CA0025; 
elseif CA==0.5  matrice_cartesian=CA0050;
end

However, you should be avoiding exact comparison of floating point values. The values 0.25 and 0.5 are exactly representable in floating point but the value that is in CA might have been calculated by a process that did not result in exactly 0.25 or exactly 0.5

http://matlab.wikia.com/wiki/FAQ#Why_is_0.3_-_0.2_-_0.1_.28or_similar.29_not_equal_to_zero.3F