How to prevent rounding number

Question

Hoang Le Tran 2023-5-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1964574-how-to-prevent-rounding-number

评论： Walter Roberson 2023-5-16

Hello everyone, I have a trouble about rounding. This is my example: I assign K=173.1227 but the numerator the transfer function G is 173.1. When I try K=173.227, the num of G is 173.2. How can I fix that? I try to format long and go to preferences to adjust the variable and command windows but that doesn't work. Please help me! TIA

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Answer 1

Walter Roberson 2023-5-16

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1964574-how-to-prevent-rounding-number#answer_1236199

在 MATLAB Online 中打开

G1 = tf(173.1227, conv([1 0.2], [1 8 20]))
G1 =
 
            173.1
  --------------------------
  s^3 + 8.2 s^2 + 21.6 s + 4
 
Continuous-time transfer function.
format long g
G1.numer
ans = 1×1 cell array
    {[0 0 0 173.1227]}

The transfer function itself is not using the rounded values. The rounded values are only for display purposes.

The internal code does not offer any way to configure the number of significant digits: it always uses %.4g format for non-integers.

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Hoang Le Tran 2023-5-16

在 MATLAB Online 中打开

Can I ask you a question about K? I use the command Margin to find the k neutral limitation. And I assign the K into the transfer function to test is the K right?.

G=tf([1],conv([1 0.2],[1 8 20]))
G =
 
              1
  --------------------------
  s^3 + 8.2 s^2 + 21.6 s + 4
 
Continuous-time transfer function.
K=margin(G)
K = 173.1227

But unfortunately, it is not right 100%. Can you help me?

Walter Roberson 2023-5-16

在 MATLAB Online 中打开

Sorry, I am not familiar with margin or "k neutral limitation"

format long g
G=tf([1],conv([1 0.2],[1 8 20]))
G =
 
              1
  --------------------------
  s^3 + 8.2 s^2 + 21.6 s + 4
 
Continuous-time transfer function.
K = margin(G)
K = 
          173.122670692379