plot being generated is not in log space

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M K P Dev 2021-7-15

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/879503-plot-being-generated-is-not-in-log-space

评论： M K P Dev 2021-7-22

采纳的回答： Cris LaPierre

I am plotting a curve for the following model:

fitfun = fittype(@(a0,a1,x) a0+(a1.*x));

The x and y values are log(x1) and log(y1). I have configures as YScale='log' and XScale='log'

y = [2.091666958,1.929444472,1.954580163,1.903415586,1.875379629,1.875379629,1.903415586,1.875379629,1.942330552,1.903415586,1.903415586,1.929750906,1.942330552]'

x = [7.163732175,7.009281649,5.203296758,7.0004477,7.087439702,7,7.012988611,7.002354474,5.274252552,5.38274806,7.000976802,7,5.321121833]'

UIAxes = uiaxes

UIAxes.XGrid = 'on';

UIAxes.YGrid = 'on';

UIAxes.XMinorGrid = 'on';

UIAxes.YMinorGrid = 'on';

UIAxes.YScale='log';

UIAxes.XScale='log';

starting_x = [1 1];

fitfun = fittype(@(a0,a1,x) a0+(a1.*x));

[fitobject,gof,output] = fit(x,y,fitfun,'StartPoint',starting_x);

fig = figure('Visible','off');

ax = axes(fig);

FigHandle = plot(fitobject,x,y,'or');

hApp = copyobj(FigHandle, UIAxes);

but still the plot which is being plotted is in linear scale and not log scale

I expect the output in log scale:

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Answer 1

Cris LaPierre 2021-7-15

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https://ww2.mathworks.cn/matlabcentral/answers/879503-plot-being-generated-is-not-in-log-space#answer_747688

编辑：Cris LaPierre 2021-7-15

在 MATLAB Online 中打开

That's an interesting way to get a plot into a UIAxes. Is there a reason why you don't just plot into it directly?

Your axes are still in log, but by default MATLAB sets the X and Y limits so that your data fills the graph. In your case, there is such little variance in your X and Y data that it looks linear. Set the X and Y limits to [1 10] to convince yourself they are still in log scale.

hApp = copyobj(FigHandle, UIAxes);  
ylim(UIAxes,[1 10])
xlim(UIAxes,[1 10])

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Cris LaPierre 2021-7-17

编辑：Cris LaPierre 2021-7-17

在 MATLAB Online 中打开

I assume the issue is that your plot command cannot contain a fit object and a target axes. In this case, you could use feval to create your fit line, then a plot command with a target axis. I'll assume you've added an axes component to your app canvas already, and named it UIAxes

fitfun = fittype(@(a0,a1,x) a0+(a1.*x));
starting_x = [1 1]; 
fitfun = fittype(@(a0,a1,x) a0+(a1.*x));     
[fitobject,gof,output] = fit(x,y,fitfun,'StartPoint',starting_x);
fy = feval(fitobject, x);
loglog(app.UIAxes,x,y,'ro',x,fy,'r-')
ylim(app.UIAxes,[1 10])
xlim(app.UIAxes,[1 10])