tailieunhanh - MATLAB Demystified phần 9

thêm chúng vào, và trả về kết quả là một số nguyên. Lớp trở lại của Địa chỉ sẽ được "số nguyên." Khi xác định các lớp học trở lại, bạn có thể sử dụng được xây dựng trong các loại dữ liệu của chương trình ngôn ngữ, chẳng hạn như string, char, hoặc số nguyên hoặc sử dụng các lớp học mà bạn đã xác định trong mô hình Rose của bạn. | 254 MATLAB Demystified Figure 10-6 Plot of a third order polynomial fit Now let s find A A sum w-temp . 2 A We find r2 to be r2 1 - A S r2 It looks like we have a perfect fit to the data. However this is misleading and in fact the real function describing this data is T 100 .23t - Let s have MATLAB print the r-squared value in long format format long r2 r2 CHAPTER 10 Curve Fitting 255 J Well the fit is extremely accurate as you can see from the plot. Let s compute the RMS. RMS sqrt sum 1 N w-temp .A2 RMS The RMS is less than one so we can take it to be a good approximation. Now that we have a function y t we can estimate the temperature at various times for which we have no data. For instance the data is collected out to a time of 7 hours. Let s build the function out to longer times. First we extend the time line t 0 15 Regenerate the fit polynomial y a t. 3 b t. 2 c t d We can use the find command to ask questions about the data. For instance when is the temperature less than 80 degrees so maybe we can risk picking up the metal block find y 80 ans 148 149 150 151 The command find has returned the array indices for temperatures that satisfy this requirement. We can reference these locations in the array t that contains the times and the array y that contains the temperatures. First we extract the times adding a quote mark at the end to transpose the data into a column vector A t 148 151 A T- 256 MATLAB Demystified Now let s get the corresponding temperatures B y 148 151 B We can arrange the data into a two column table with the left column containing the times and the right column the temperatures Table A B Table So for instance we see that at hours the block is estimated to be at about 75 degrees. Now let s generate a plot of the data from 10 hours to