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gibson:teaching:fall-2014:math445:lecture6-diary [2014/09/18 12:16]
gibson [Graphical data analysis of log-linear relations]
gibson:teaching:fall-2014:math445:lecture6-diary [2014/09/18 12:21]
gibson [Graphical data analysis of log-linear relations]
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 ===== Graphical data analysis of log-linear relations ===== ===== Graphical data analysis of log-linear relations =====
  
-<code matlab>​ +==== example 1: a linear relationship ​====
-======================================================================= +
-% Ok. Let's move on the graphical data analysis+
  
 +<code matlab>
 % Load datafile '​data1.asc'​ into matlab with '​load'​ command % Load datafile '​data1.asc'​ into matlab with '​load'​ command
 >> D = load('​data1.asc'​); ​ >> D = load('​data1.asc'​); ​
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 <code matlab> <code matlab>
-% Perfect! ​The functional relation between y and x is y = -0.49 x + 19+% Perfect! ​So the functional relation between y and x is y = -0.49 x + 19 
 +</​code>​
  
 +==== example 2: a log-linear relationship ====
  
-Ok, let's move on the the next data file and try to figure out its y = f(x) relation. ​+<code matlab>​ 
 +Load the next data file and try to figure out its y = f(x) relation. ​
 >> D = load('​data3.asc'​);​ >> D = load('​data3.asc'​);​
 >> xdata = D(:,1); >> xdata = D(:,1);
 >> ydata = D(:,2); >> ydata = D(:,2);
->> plot(xdata, ydata,'​mo-'​);​ grid on+>> plot(xdata, ydata,'​mo-'); xlabel('​x'​);​ ylabel('​y'); grid on
 </​code>​ </​code>​
 +
 +{{ :​gibson:​teaching:​fall-2014:​math445:​logplot0.png?​nolink&​400 |}}
  
 <code matlab> <code matlab>
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 >> semilogy(xdata,​ ydata, '​mo-'​);​ xlabel('​x'​);​ ylabel('​y'​);​ grid on >> semilogy(xdata,​ ydata, '​mo-'​);​ xlabel('​x'​);​ ylabel('​y'​);​ grid on
 </​code>​ </​code>​
 +
 +{{ :​gibson:​teaching:​fall-2014:​math445:​logplot1.png?​nolink&​400 |}}
  
 <code matlab> <code matlab>
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 >> semilogy(xdata,​ ydata,'​mo-',​ x, 400*10.^(-0.1*x));​ xlabel('​x'​);​ ylabel('​y'​);​ grid on >> semilogy(xdata,​ ydata,'​mo-',​ x, 400*10.^(-0.1*x));​ xlabel('​x'​);​ ylabel('​y'​);​ grid on
 </​code>​ </​code>​
 +
 +{{ :​gibson:​teaching:​fall-2014:​math445:​logplot2.png?​nolink&​400 |}}
  
 <code matlab> <code matlab>
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 </​code>​ </​code>​
  
 +{{ :​gibson:​teaching:​fall-2014:​math445:​logplot3.png?​nolink&​400 |}}
  
 <code matlab> <code matlab>
 % so the functional form is y = 700 * 10^(-0.085 x).  % so the functional form is y = 700 * 10^(-0.085 x). 
 +
 +% Don't ask me why Matlab keeps changing the grid lines on the logarithmic plots... ​
 </​code>​ </​code>​
gibson/teaching/fall-2014/math445/lecture6-diary.txt · Last modified: 2014/09/18 12:21 by gibson