Calculating Error and intercept on a log plot

3 views (last 30 days)
Hi there,
this is the code/ data I have. Please note I have already taken the logs so that the data is scaled appropriately.
Log_N = [1.09861228866811,1.09861228866811,1.79175946922806,2.56494935746154,3.61091791264422,4.23410650459726,4.65396035015752];
Log_R = [-2.50000000000000,-2,-1.50000000000000,-1,-0.500000000000000,0,0.500000000000000];
plot(Log_R,Log_N,'o')
hold on
title('Correlation Dimension')
xlabel('Log R')
ylabel('Log Nd')
hold on
[P, S,] = polyfit(Log_R,Log_N,1);
% Evaluate the fitted polynomial p and plot:
f = polyval(P,Log_R);
plot(Log_R,Log_N,'o',Log_R,f,'-')
legend('data','linear fit')
I have created my line of best fit using polyfit and polyval. All I am wanting to do is fit a straight line to my data and would like to know my gradient of the line/ slope and the associated error.
Any advice would be much appreciated.
I tried using 'fit'
[curve, ~] = fit(Log_R, Log_N,'poly1');
but the errors I got were:
>> correlation_attempt_2
Error using fit>iFit (line 127)
X must be a matrix with one or two columns.
Error in fit (line 108)
[fitobj, goodness, output, convmsg] = iFit( xdatain, ydatain, fittypeobj, ...
Error in correlation_attempt_2 (line 72)
[curve, ~] = fit(Log_R, Log_N,'poly1');

Accepted Answer

KALYAN ACHARJYA
KALYAN ACHARJYA on 17 Apr 2019
Edited: KALYAN ACHARJYA on 17 Apr 2019
ERROR
Error using fit>iFit (line 127)
X must be a matrix with one or two columns.
Error in fit (line 108)
[fitobj, goodness, output, convmsg] = iFit( xdatain, ydatain, fittypeobj, ...
Error in ans_matlab_april19 (line 17)
Threfore I did transpose
[curve, ~]=fit(Log_R', Log_N','poly1');
figure, plot(curve,Log_R,Log_N)
66.png
  1 Comment
P_L
P_L on 18 Apr 2019
Edited: P_L on 18 Apr 2019
Many Many thanks!! solved my problem!
I am trying to amend my data points so that appear larger- the 'MarkerSize' command isn't working - is there another way I need to do it?
This is what I am trying:
figure, plot(curve,Log_R,Log_N,'o','MarkerSize',12, 'MarkerFaceColor', 'b')

Sign in to comment.

More Answers (0)

Categories

Find more on Descriptive Statistics in Help Center and File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!