Error Using Rainflow fonction

Hello everyone,

I'm not really good at Matlab, but I need to use it to process some load cycles result using the rainflow function (please see attachment)

I have written the code as below

clear all,
clc,
[filename,pathname] = uigetfile({'*.xlsx;*.xlsm','Excel Worksheets (*.xlsx,*.xlsm)'},'Select File');
[file,sheets] = xlsfinfo([pathname,filename]); 
num_1 = xlsread(filename);

[num_3, txt]= xlsread(filename);

%read only row and column with number
Data_1 = num_3(4:end,:); % 4:end, --> choose all the row start from 4 % : --> choose all the column % start at row 4 and read all column

X = num_3(4:end,7);  % 4,--> Choose only row 4 seread oly row 4 and all column. 
Y = num_3(4:end,6);
Z = num_3(4:end,8);


figure(1)

plot3(X,Y,Z);

t = linspace(min(Y),max(Y),length(Z)/10);
d = linspace(min(Y),max(Y),length(Z)/5);

figure(2)

Z = [X Y]

rainflow(Z,t);

and unfortunately have the errors below after the code:

Error using rainflow

Expected X to be a vector.

Error in rainflow>parseInputs (line 184)

validateattributes(x,{'single','double'},...

Error in rainflow (line 81)

[x,t,ext,td] = parseInputs(x,varargin{:});

Error in KW31_BMW_Load_Cycle_Ju (line 39)

rainflow(Z,t)

Can someone please tell me were I´making the mytake by using the Rainflow function?

Thank in advance

Answer 1

[Animesh]

Hey @JoeTeg

The "rainflow" function is typically used for fatigue analysis and expects a time history of stress or strain as input. Thus the provide input should be a vector.

The current code is passing a matrix "Z" composed of "X" and "Y" values, making "Z" a 51 x 2 matrix, which is unsuitable for the "rainflow" function.

If you wish to concatenate data of "X" and "Y", try using "vertcat" function to concatenate them vertically.

Z = vertcat (X,Y)

You can refer the following MathWorks documentation for more information :

https://www.mathworks.com/help/signal/ref/rainflow.html

[JoeTeg]

Hys @Animesh,

Thank a lot for the answer.

like you saided, i want to use the rainflow to evaluate 3 load cylles using the folowing data of the the attachment.

X = num_3(4:end,7); % 4,--> Choose only row 4 seread oly row 4 and all column.

Y = num_3(4:end,6);

Z = num_3(4:end,8);

when i try the exemple show in this link below, it work, but when use the code up, even by replacing Z = [X Y] with Z = vertcat (X,Y), it still doesn 't work.

The reason whyle i used Z = [X Y] is because from wat i unterstood the rainflow can only take twoo argument. what i want to plot is the

rainflow (X,Y,Z).

How can i please implement it ?

Thank in Advance

https://www.mathworks.com/help/signal/ref/rainflow.html

[Animesh]

Hey @JoeTeg

From what I can gather, you want to evaluate three load cycles together. The "rainflow" function in MATLAB is designed to process a single vector of data, typically a time history of stress or strain. It cannot directly handle three separate vectors like "X", "Y", and "Z" simultaneously.

Here's a way to approach it: combine the data. If you need to evaluate the load cycles for the combined data, you need to create a single vector that represents the load history. This could be done by concatenating the vectors "X","Y", and "Z" in a meaningful way.

% Read only row and column with number
Data_1 = num_3(4:end, :); % 4:end, --> choose all the rows starting from 4 % : --> choose all the columns
X = num_3(4:end, 7);  % Column 7
Y = num_3(4:end, 6);  % Column 6
Z = num_3(4:end, 8);  % Column 8

% Combine X, Y, Z into a single vector
combinedData = [X; Y; Z];

Also make sure that the time vector "t" has same dimensions as the transpose of "combinedData".

t=linspace(0, length(combinedData)-1, length(combinedData));

Now, you can evaluate "rainflow" on this data:

rainflow(combinedData, t);

[JoeTeg]

thank a lot @Animesh for taking from your time to help me. I really appreciate it. I will try the code a let you know if i stil have some questions.

Answer 2

[Star Strider]

The rainflow function only takes vector arguments.

What result do you want?

In the interim,try this —

T1 = readtable('Data_for_Rainflow.xlsx', 'VariableNamingRule','preserve')

T1 = 52x8 table
    Zeit    Pressure_1    Pressure_2    Masse Flow    Pressure_3    adiabatic power    Normlize Load    Cycle 1 to 3
    ____    __________    __________    __________    __________    _______________    _____________    ____________

    NaN          NaN           NaN           NaN           NaN              NaN               NaN           NaN     
      0       102.01        97.432        5.0249        1.0747         0.031449          0.023871             1     
    0.5       140.42        111.94         36.53         1.486           1.3174                 1             2     
      1       140.41        111.94        36.511        1.4859           1.3167           0.99942             3     
    1.5       139.69        111.58        35.947         1.478           1.2779              0.97             1     
      2       138.72         111.1        35.198        1.4675           1.2271           0.93142             2     
    2.5       137.88        110.68        34.546        1.4584           1.1836           0.89844             3     
      3       137.17        110.33        33.991        1.4506           1.1472            0.8708             1     
    3.5        136.5        110.03        33.446        1.4433           1.1127           0.84463             2     
      4       135.89        109.78        32.948        1.4368            1.082           0.82129             3     
    4.5       135.18        109.48        32.375        1.4292           1.0468           0.79459             1     
      5       134.48        109.18        31.809        1.4217           1.0127           0.76866             2     
    5.5       133.86        108.91        31.301         1.415          0.98236           0.74566             3     
      6       133.26        108.66        30.817        1.4086          0.95389           0.72405             1     
    6.5       132.94        108.52        30.556        1.4052           0.9388            0.7126             2     
      7        132.7        108.42        30.361        1.4026          0.92756           0.70406             3     

VN = T1.Properties.VariableNames;

num_3 = T1{2:end,:};
X = num_3(:,7);  % 4,--> Choose only row 4 seread oly row 4 and all column. 
Y = num_3(:,6);
Z = num_3(:,8);
t = num_3(:,1);

figure(1)
plot3(X,Y,Z);
grid  on
xlabel(VN{7})
ylabel(VN{6})
zlabel(VN{8})

% t = linspace(min(Y),max(Y),length(Z)/10);
d = linspace(min(Y),max(Y),length(Z)/5);

figure(2)
Z = [X Y]

Z = 51x2

0.0239 0.0314 1.0000 1.3174 0.9994 1.3167 0.9700 1.2779 0.9314 1.2271 0.8984 1.1836 0.8708 1.1472 0.8446 1.1127 0.8213 1.0820 0.7946 1.0468

<mw-icon class=""></mw-icon>

<mw-icon class=""></mw-icon>

figure
rainflow(Z(:,1),t)
sgtitle(VN{7})

figure
rainflow(Z(:,2),t);
sgtitle(VN{6})

.

[JoeTeg]

Thank a lot @Star Strider for taking for your help. I learned a new way to read date from Excel. I will try the code a let you know if i stil have some questions.

[Star Strider]

My pleasure!

It would be relatively straightforward to plot thte ‘load reversal’ plots together in the same axes, however I doubt that it would be possible to do the same with the histograms. If you return the outputs:

[c,rm,rmr,rmm,idx] = rainflow(___)

it might be possible to combine them in some way, although that is not obvious to me, since I am not certtain what result you want.

[JoeTeg]

Thx i will try it and come back to you with more detaisl. It is also the first time for me to process such kind of data

i wish you a nice evening

[Star Strider]

Thank you!

I have never needed to use that function either, ono my own data. I am learning as well.