calculation of average and difference from imported data

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Am looking at plotting the graph for P vs exposure time, P vs stress, and P vs time vs stress(all in one graph), and finally calculate the cumulative value for P as captured in the equation 1 below
The values for stress and exposure time is read from a .xy file format ( i atatched it here as a .txt file) with two columns and a long list of rows. Let’s say 2000 rows with different values for time and stress at every point.
The expression for D is captured below
P = F x stress^a + time^b….. ………..(1)
Where
a, has a constant value of 2.416
b has a constant value of 0.785
And F with a constant value of 3.62 x 10-7
Please note: The values of (stress) and t (exposure time) is read from a file. But the computation required to get the exact value of stress and time from the read file is
current value for shear stress=(current row+previous row)/2------------------(2)
current value for exposure time=current time-previous time=∆t---------(-3)
Put the calculated values for each current value of time and stress to calculate the D values based on equation 1
please how do i go about implementing this in matlab. i have imported the attached diument in MATLAB, seperating this variables and implementing the above equations for 2 and 3 for this sets of values is a challenge. can any one guide me.
  8 Comments
Rik
Rik on 26 Aug 2020
Deleted question and comments posted by Victor Albert as far as I was able to retrieve it from Google cache (WBM link to cache):
calculation of average and difference from imported data
Am looking at plotting the graph for P vs exposure time, P vs stress, and P vs time vs stress(all in one graph), and finally calculate the cumulative value for P as captured in the equation 1 below
The values for stress and exposure time is read from a .xy file format ( i atatched it here as a .txt file) with two columns and a long list of rows. Let’s say 2000 rows with different values for time and stress at every point.
The expression for D is captured below
P = F x stress^a + time^b….. ………..(1)
Where
a, has a constant value of 2.416
b has a constant value of 0.785
And F with a constant value of 3.62 x 10-7
Please note: The values of (stress) and t (exposure time) is read from a file. But the computation required to get the exact value of stress and time from the read file is
current value for shear stress=(current row+previous row)/2------------------(2)
current value for exposure time=current time-previous time=∆t---------(-3)
Put the calculated values for each current value of time and stress to calculate the D values based on equation 1
please how do i go about implementing this in matlab. i have imported the attached diument in MATLAB, seperating this variables and implementing the above equations for 2 and 3 for this sets of values is a challenge. can any one guide me.
_____________________________
Victor Albert on 21 Aug 2020 at 15:45
dear rik
i have imported the data.
how do i get the values for equation 2 and 3 from the long list of data(file.txt) and claulcte it for each D values
i know for and while loop statements can do that, but am not sure how to implement it in matlab. i had to export the data back to excel for computation.
but i want to be bale to implement this with matlab.
_____________________________
Victor Albert on 21 Aug 2020 at 15:46
but i want to be able to implement this with matlab, considering the long list of data sets( rows and column)
_____________________________
Victor Albert on 21 Aug 2020 at 18:41
% reading the file
fidi = fopen('file.xy','rt'); % to open the file and save it to a variable
% named fidi
st = fseek(fidi, 1, 'bof'); % Position File After First Line
k1 = 1; % Counter
while (st == 0) && (~feof(fidi)) % Test For End Of File Or Unsuccessful ‘fseek’ File Position
particle{k1} = textscan(fidi, '%f%f', 'Delimiter','\t', 'HeaderLines',4, 'CollectOutput',1);
st = fseek(fidi, 50, 'cof'); % Position File Pointer To Next Line After Stop
k1 = k1 + 1;
end
% function creation
function P = damage(time,stress)
a = 2.416;
b = 0.785;
f = 3.62*10^-7;
P = f* (stress^a) + (time^b);
end
_____________________________
Victor Albert on 21 Aug 2020 at 20:03
thats what i have written
_____________________________
Victor Albert on 22 Aug 2020 at [about 8:30]
file.txt is what i meant
_____________________________
Victor Albert on 22 Aug 2020 at [about 11:30]
the first column contains the time values and the second the stress values. this data were imported from a simulation done in Ansys fluent. there were 60 particles with each having certain number of stress and time values. i hope it clarifies.
particle 1
time stress
0 1.98974
2.51387e-05 2.00879
5.02775e-05 2.04566
7.50753e-05 2.06206
9.98731e-05 2.05735
0.000124671 2.05541
_____________________________
Victor Albert on 22 Aug 2020 at [about 12:30] [scalarvstime1.csv was attached to this comment]
i hope the attached help you. attached documents were only sent to excel to remove the strings.

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Answers (1)

Rik
Rik on 22 Aug 2020
Well, if that is the input, then this edit to your function should work:
function P = damage(time,stress)
a = 2.416;
b = 0.785;
f = 3.62*10^-7;
P = f* (stress.^a) + (time.^b);
% ^ ^
% use element-wise power, instead of matrix multiplication
end
  13 Comments
Victor Albert
Victor Albert on 27 Aug 2020
i tried to run the above code. this is the error i am still getting. what could go wrong here.
Rik
Rik on 27 Aug 2020
You can't have a function inside a script file with the same name.

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