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David Wilson


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Auckland University of Technology

104 total contributions since 2011

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Answered
Filling the area between curves (loglog)
I too had some difficulty to do this elgantly. I changed the name of your data file, and commented out the material that didn't ...

2 months ago | 0

Answered
How to solve the riccati equations in matlab
Well, if Google translate is accurate, you seem to want to solve for the matrix Q. I'm assuming that everything is a matrix w...

2 months ago | 1

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Answered
How to solve the riccati equations in matlab
Do you have the control toolbox? I suspect that you could use are.m and related friends.

2 months ago | 0

Answered
How to find time constants from given 2+ order transfer function?
If you just want to display the transfer function in time-constant form, you can do the following: s = tf('s'); k = 45; % an...

2 months ago | 0

Answered
i am trying to made a code to int the numbers of time i want
Remove the z=x^2 from the loop. syms x n y z a; n= 5 z=x^2; for y=1:n z=int(z) end

6 months ago | 1

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Answered
How to obtain regression polynomial equation with more than 2 independent variables with degree 5.
OK, the fitting is easy, the plotting less so. Since you didn't give us too many hints, not did you give us any data to work wit...

7 months ago | 2

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Answered
Text keeps going behind topographic map
Your mountains are covering the text (as they should). So you need to write your text above the highest peak, so that it is seen...

7 months ago | 0

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Answered
function to produce line graph
I would strongly suggest you don't try a polynomial fit here. From the context (which you neglected to tell us), I suspect that ...

7 months ago | 0

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Answered
creating a transfer function from a determinant
How about: [num,den] = numden(G_vel) G_vel_tf = tf(sym2poly(num), sym2poly(den))

11 months ago | 0

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Answered
Problem Calculating Nonlinear Indefinite Integral
Since you neglected to tell us values for a and b, I'll just set them to a=2 and b=1. You have also two definitions for g(x), so...

11 months ago | 0

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Answered
Plot electric potential distribution
Well I kind of get what you want, but you do seem to have a singularity at the origin when r=0. p = 1; sig = 1; % constants th...

12 months ago | 1

Answered
fitting scatter data into multiple cosine functions
Yes, but it is always tricky to fit such sinusoids without good starting estimates. I'm going to use lsqcurvefit from the optimi...

1 year ago | 0

Question


Is the Moving Variance block in Simulink vectorised?
I'm using the Moving Variance block in Simulink and it seems to be giving unexplained results for vectorised (muxed) inputs. My ...

1 year ago | 1 answer | 0

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answer

Answered
2D Convolution - Sobel Filter. What is wrong?
Here's my (old) code for a sobel filter: img = imread('Davis_Hall.jpg'); % 'Davis_Hall.jpg':color image X =double(rgb2gray(i...

1 year ago | 0

Answered
Related to Matlab Step Comment
You are possibly confusing the closed loop response with the open loop. The closed loop gain is 1/4, so the error is 1-1/4 = 3/4...

1 year ago | 1

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Answered
how to solve matrix differential equation
Here's my attempt: M = [ 97227/21875, 0, 82269/109375, 0, 67311/43750, 0, -97227/218750, 0; ... 0, 97227/21875, 0, 822...

1 year ago | 1

Answered
From Fir2 output to transfer function
tr_fun should be a discrete transfer function, (not continuous) say tr_fun=tf(BF,1,1); % Generate a DISCRETE Transfer Function...

1 year ago | 0

Answered
How to identify corners of data plotted to estimate data between corners
How about using interp1 with the 'pchip' option? You did speculate the interpolation is overly complex, but then again it is onl...

1 year ago | 1

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Answered
How I can find co ordinates of intersection of two curves ?
Oh, looks like this is a common question: See (from 2016)https://au.mathworks.com/matlabcentral/answers/318475-how-to-find-the-i...

1 year ago | 1

Answered
Iterative Method of solving multiple variables without using the curvefit tool
Here's my attempt at fitting uusing lsqcurvefit from the optimisation toolbox. First I generate some synthetic data to subsequ...

1 year ago | 0

Answered
how can i calculate the angle of each gradient and x axis?
You could always differentiate to get the slope and then take the arc-tan. syms x real s = 1/(1 + exp(-2*(x-4))) dsdx = dif...

1 year ago | 0

Answered
Extracting the daily time series from a text file to a single column
A quick hack is: fname = 'D59.txt' Flow = []; fid=fopen(fname); Yr = 2012; R = []; while 1 tline = fgetl(fi...

1 year ago | 0

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Answered
How to Rearrange data?
Try something like the following: First read in the data file (which I've called numData.txt). I've used your test data above. ...

1 year ago | 0

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Answered
(Food for Thought) Peak Detection on ECG signal
OK, here's my (ugly) solution (withou using findpeaks). I've re-named your data set, and did some pre-processig. load ecg y =...

1 year ago | 0

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Answered
Simulating a FIR filter
Use the filter command. In this case your denominator, (A), coefficients are just 1. x = [ 0 0 0 1 1 1 1 1 ]' % input b = [...

1 year ago | 1

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Answered
Obtain input knowing output and transfer function
Since you have a simple transfer function, here's what I would do. (1) First generate some data that we will subsequently try ...

1 year ago | 0

Answered
curve fitting of non linear data for strain-time of creep experiment
Here's my attempt: load data1 t = time; e = strain; plot(t,e) %% Now try curve fit creep = @(p, t) p(1)*(1-exp(-p...

1 year ago | 0

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Answered
Trouble with time delay differential equation
I've only made one small change to your function. You have tried to index a non-integer number back, but the "Z" variable holds ...

1 year ago | 0

Answered
How can I simultaneously solve for these equations?
If you have the symbolic toolbox, a straight forward approach works, although it takes some time ... % ODE propblem syms B...

1 year ago | 0

Answered
Error when using ode15
It is good practice to try and avoid globals, but rather pass them as auxilary variables into the function. Fao = 1487.351; % ...

1 year ago | 0

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