joining various points when using a for loop.

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s 2015-9-24

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https://ww2.mathworks.cn/matlabcentral/answers/244941-joining-various-points-when-using-a-for-loop

评论： Star Strider 2015-9-25

for p=0:0.05:1
     h=p*log(1-p)
     plot(p,h)
end

For the above code i am trying to join the discrete points but i am unable to do so.i used line command but still i get discrete points only i am unable to connect them.

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Star Strider 2015-9-25

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/244941-joining-various-points-when-using-a-for-loop#answer_193640

编辑：Star Strider 2015-9-25

在 MATLAB Online 中打开

I would eliminate the loop and take advantage of MATLAB’s vectorisation capabilities:

p = 0:0.05:1;
h = p.*log(1-p);
figure(1)
plot(p,h)

This uses element-wise operations (denoted by the dot operator in (.*)). See the documenataion for Array vs. Matrix Operations for details.

the equation is given in a TB.Using MATLAB, plot the entropy of the binary data source as a function of p = Pr[1], when p = 0, 0.05, 0.10, . . . , 0.95, 1.0. Note that Pr[0] = 1- p. Show that the maximum entropy is achieved when p = 0.5. Make sure that the entropies of p = 0 and 1 are plotted.So i need the graph to be plotted such that it touches 0 and 1.but i am not allowed to use 0 as a index in matlab.pls help me

Star Strider 2015-9-25

在 MATLAB Online 中打开

You can either do the function form I provided, or the straight vectorised equation for h Image Analyst provided. Both give you exactly what you want, with the plot. Considering you want h(0), I would use the function form to get it.

Notice that the function form is not an array, so h(0) is the function of h at 0, not the 0 index of an array.

To get the value of the array h where p=0, do this:

p = 0:0.05:1;
h = -p.*log2(p)-(1-p).*log2(1-p);
p0 = find(p == 0);
hp0 = h(p0)

However hp0 is NaN because log2(0) does not exist, and will not plot at that point.

If the equation you provided is correct, this instruction ‘Make sure that the entropies of p = 0 and 1 are plotted.’ is in error, because the entropy at p=0 does not exist.

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