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POf seems to be always positive in the MATLAB code, but in my Python code, f also gets negative values
 

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  1. POf seems to be always positive in the MATLAB code, but in my Python code, f also gets negative values
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    <p>How to convert the <a href="http://pastebin.com/fZe0AZQn" rel="nofollow">following MATLAB</a> code to Python? <a href="http://pastebin.com/gFcr8HGR" rel="nofollow">Here is my solution</a>, but it doesn't quite produce the same results. For example, <code>f</code> seems to be always positive in the MATLAB code, but in my Python code, <code>f</code> also gets negative values.</p> <p>Any ideas how to fix the program?</p> <p>Mostly, I am concerned about these:<br> MATLAB: </p> <pre><code> for k = 1 : nx j = k+2; </code></pre> <p>Python: </p> <pre><code>for k in range(1,nx+1): j = k+2 </code></pre> <p>MATLAB: </p> <pre><code> [V,D] = eig(A, B); DD = diag(D); keep_idxs = find( ~isinf(DD) ); D = diag( DD(keep_idxs) ); V = V(:, keep_idxs); [lambda, idx] = min(diag(D)); f = V(:,idx); </code></pre> <p>Python: </p> <pre><code>w,vr = scipy.linalg.decomp.eig(A,B) w = w.real vr = vr.real w = w[2:-1-2] lambda_ = w.min() idx = w.argmin() f = vr[:,idx] </code></pre> <p>MATLAB: </p> <pre><code> f = f(3:end-2); [nf, nf_idx] = max(abs(f)); % L_infty norm n2 = f(nf_idx); % normalize sign away, too f = f ./ n2; </code></pre> <p>Python: </p> <pre><code>f = f[2:-1-1] nf = max(np.absolute(f)) nf_idx = np.absolute(f).argmax() nf_idx = np.ma.argmax(f) n2 = f[nf_idx] f = f/n2 </code></pre> <p>MATLAB: </p> <pre><code> xx = -kappa:h:kappa; </code></pre> <p>Python: </p> <pre><code>xx = np.arange(-kappa, kappa+h, h) </code></pre> <p>Are those equivalent with each other? If they are, then why don't they produce exact the same results?</p>
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    1. USJoachim Sauer
    1. USuser569474
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      1. POf seems to be always positive in the MATLAB code, but in my Python code, f also gets negative values
      1. USuser569474
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    2. VO
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      1. POf seems to be always positive in the MATLAB code, but in my Python code, f also gets negative values
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      1. POf seems to be always positive in the MATLAB code, but in my Python code, f also gets negative values
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    1. COYou need to format your code correctly, and be more specific about your problem. What are you talking about?
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      1. POf seems to be always positive in the MATLAB code, but in my Python code, f also gets negative values
      1. USFalmarri
    2. COThe syntax is quite different. In MATLAB indices start from 1, in Python they start from 0. I want to know if I have made any errors that will produce different results.
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      1. POf seems to be always positive in the MATLAB code, but in my Python code, f also gets negative values
      1. USuser569474
    3. COI try to solve numerically an eigenvalue problem. The code is in MATLAB and I try to convert it to Python.
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      1. POf seems to be always positive in the MATLAB code, but in my Python code, f also gets negative values
      1. USuser569474
 

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