MATLAB Practice questions solution

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Ali Awada
Ali Awada 2021-1-3
评论： DEEPAK RAJ B 2024-1-20
Hello all,
I am new to MATLAB and I am still trying to learn it by myself. I was trying to solve the questions posted by MATLAB. I know I didn't use the double function as suggested so please enlighten me with your ideas and let me know if i was at least close to what the problem is asking for:
Problem(link: https://www.mathworks.com/services/training/certification/ml-professional-exam/practice-test.html)
The provided text file (readings.txt) contains a timestamp broken up into year, month, day, hour, minute, second, and timezone components, as well as a reading from a sensor. Write a script that reads the data from the file using the textscan function.
The script must:
  • Convert the timestamps into single numeric serial date numbers stored in a variable named dates
  • Ignore the timezone component of the timestamp by not reading it into the workspace
  • Place numeric values for the readings in a single array of type double with a variable name of readings
clc
clear all
fileID1 = fopen('readings.txt');
dates = textscan(fileID1, '%s %s %s %s %s %s %s %s');
fclose(fileID1);
whos dates;
celldisp(dates)
fileID2=fopen('readings.txt')
C=textscan(fileID2, '%q %q %q %q %q %q %*q %q');
fclose(fileID2);
whos C;
celldisp(C)
fileID3=fopen('readings.txt');
D=textscan(fileID3,'%*q %*q %*q %*q %*q %*q %*q %q');
fclose(fileID3);
whos D;
celldisp(D)

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回答（3 个）

Image Analyst
Image Analyst 2021-1-3
Perhaps datenum()?
>> d=datenum(now)
d =
738159.473416505
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Image Analyst
Image Analyst 2021-1-10
Then just use the first 3 lines and skip the rest of the lines that have to do with plotting.
Ali Awada
Ali Awada 2021-1-11
the problem asks us to use the function textscan

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Kazem Gheysari
Kazem Gheysari 2021-8-24
编辑：Kazem Gheysari 2021-8-24
clear
fileID = fopen('readings.txt');
C_text = textscan(fileID,'%s',8,'Delimiter',' ');
C = textscan(fileID,'%f %f %f %f %f %f EST %f','Delimiter',' ','EmptyValue',-Inf);
fclose(fileID);
Y = C{1,1};
M = C{1,2};
D = C{1,3};
H = C{1,4};
MN= C{1,5};
S = C{1,6};
dates = datenum(Y,M,D,H,MN,S)
readings = C{1,7};
matlab1.com
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Image Analyst
Image Analyst 2021-8-24
What is matlab1.com? (I did not click your link because there is no explanation)

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Abhiram Rayidi
Abhiram Rayidi 2022-6-27
Ran in:
syms y(t);
dsolve(diff(y)==y, y(0)==1, 'Expansion Point', 0)
Error using symengine
Unexpected 'identifier'.

Error in mupadengine/evalin_internal

Error in dsolve>mupadDsolve (line 333)
sys = [sys_sym reshape(evalin_internal(symengine, sys_str), 1, [])];

Error in dsolve (line 203)
sol = mupadDsolve(args, options);

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