MATLAB: Newbie question

array tanh barrier insertion loss fresnel maekawa

Hi – just started using Matlab.

I've got this array of values: – Nvalues =

    1.3138    5.0076    3.2438    3.2438    0.7919    4.4857    2.7220    6.4158

and I need to make another array from those values using this formula: –

 5+20*log((sqrt(2*pi*Nvalues))/tanh(sqrt(2*pi*Nvalues)))

but when I put in that formula it just gives me one value – 34.9308. What I want is a new array of values – the first based on the above equation, where the two Nvalues in the equation are both the first one in the list, the 2nd based on the above equation, where the two Nvalues are both the 2nd one in the list, and so on.

How do I do this?

Thanks

Best Answer

5+20*log((sqrt(2*pi*Nvalues))./tanh(sqrt(2*pi*Nvalues)))

Notice './' instead of '/'.

help rdivide

./ Right array divide. A./B denotes element-by-element division. A and B must have the same dimensions unless one is a scalar. A scalar can be divided with anything.

Related Solutions

MATLAB: Array indices must be positive integers or logical values.

The error text pretty much explains why you are getting an error.

"Array indices must be positive integers or logical values"

Matlab arrays are indexed with array indices that start with 1 for the first index in the array.

You are trying to index using t= 0:142.27 which starts at zero (which is not a valid array index in Matlab). Note also that, since you have not provided a step size for constructing this vector, the last element of the vector will be 142 (not 142.27) because Matlab assumes a step size of one if you don't tell it otherwise.

You probably need to define your t vector with a step size (for example t = [0:0.01:142.27]) and then, using the fact that Matlab operates on vectors as well as scalars, you can get your answer for the whole vector at once with this:

h = (30^(5/2)-(5*sqrt(2)*9.8/2)*t).^(2/5) ;

Note that there is not a (t) on the left hand side. You correctly had the .^ instead of ^ to get element-wise operations but the left hand side can accept the entire vector result without the index.

I hope this helps.

MATLAB: Newbie question

pi is already defined; it is not a good idea to redefine it.

Remove your BG=5 line.

Immediately before you calculate Lvalues, add the line

BGs = [1 2 3 4 5 6 7 8 9 10];  %the list of values you want to use
L_pB = zeros(1,length(BGs));   %more efficient to preallocate
for K = 1 : length(BGs)
  BG = BGs(K);

Then, change your assignment that has L_pB on the left hand side, to instead of L_pB(:,K) on the left hand side. And then add the lines

end
plot(BGs, L_pB, 's')

right after that.

I have, though, not gone through the code to be sure that you only calculate a single L_pB value per BG value. If instead multiple values are calculated each time, change the 1 in the "zeros" line to be the number of items that are calculated each time (e.g., 7)

I did not join the points together in the plot because it is not clear to me that the points could be considered ordered or continuous.

Best Answer

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MATLAB: Array indices must be positive integers or logical values.

MATLAB: Newbie question

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