add lsline or trend line to log-log graph

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Nabeel 2015-3-8

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链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/182100-add-lsline-or-trend-line-to-log-log-graph

评论： Star Strider 2015-3-14

采纳的回答： Star Strider

在 MATLAB Online 中打开

i want to draw a least square line to log-log plot i am using following scripy

wet=[120 49 30 21 12 10 9 7 4];
dry=[49 12 5 1 1 1 0 0 0 ];
x1=[1 2 3 4 5 6 7 8 9];
scatter(x1,wet);
set(gca,'XScale','log');
set(gca,'YScale','log');
lsline

but it is not working. is their any other way to draw a line which is straight pass through the points

采纳的回答

Star Strider 2015-3-8

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/182100-add-lsline-or-trend-line-to-log-log-graph#answer_170517

在 MATLAB Online 中打开

This works:

wet=[120 49 30 21 12 10 9 7 4];
dry=[49 12 5 1 1 1 0 0 0 ];
x1=[1 2 3 4 5 6 7 8 9];
scatter(x1,wet);
set(gca,'XScale','log');
set(gca,'YScale','log');
b = polyfit(log(x1), log(wet), 1);
wetfit = exp(b(2)) .* x1.^b(1);
hold on
plot(x1, wetfit)
hold off

producing:

hi, i have applied the following code to my original data. wet=[807 427 268 130 83 41 27 14 5 4 2 3 1]; x1=[1 2 3 4 5 6 7 8 9 10 11 12 13]; dry=[494 332 245 150 126 78 69 48 38 35 26 21 21 22 9 9 13 7 10 3 4 5 4 3 5 3 2 3 2 1 5 1 2 4 2 3 1 1 1 1 1 1]; x2=[1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 33 34 36 37 38 40 42 44 46 48 53]; bwet = polyfit(log(x1), log(wet), 1); wetfit = exp(bwet(2)) .* x1.^bwet(1); wetslope=bwet(1); xintwet = (1/exp(bwet(2)))^(1/bwet(1)); m=length(x1)+1; x1vecwet = linspace(min(x1), xintwet, m); wetext = exp(bwet(2)) .* x1vecwet.^bwet(1); figure(1) scatter(x1,wet,'filled','k'); hold on plot(x1vecwet, wetext,'r','LineWidth',2.5,'LineStyle','--') scatter(x2,dry,'d'); set(gca,'XScale','log'); set(gca,'YScale','log'); bdry = polyfit(log(x2), log(dry), 1); dryfit = exp(bdry(2)) .* x2.^bdry(1); dryslope=bdry(1); plot(x2, dryfit,'LineWidth',2.5) hold off

it has r-squared of 0 for both wet and dry :-( (This a a rainfall wet and dry days) i am not a regular programmer....

Star Strider 2015-3-14

The code in the FEX contribution seems to use the same algorithm mine does for R-squared. Mine uses the nonlinear fit and the OLSCF (Ordinary Least Squares Cost Function) to generate the ‘norm(Y-X)’ data.

I didn’t run the FEX submission, but I trust my code.

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