call matlab function from python but the argument is always mismatch

I want to call fanbeam, the function defines in matlab like

fanbeam

proj = fanbeam(image, 1075,...
        'FanSensorGeometry', 'arc',...
        'FanSensorSpacing',0.1, ...
        'FanRotationIncrement', 360/320);

At first I call the fanbeam in python like

    proj = eng.fanbeam(image,1075.0,nargout=3)

it works well,But I want add some argument 'FanSensorGeometry', 'FanSensorSpacing',so I try to wrap them as a dict then pass the dict to fanbeam

     para_dic = {"FanSensorSpacing":0.1,"FanRotationIncrement" :360.0/320}
     proj = eng.fanbeam(hello,1075.0,para_dic,nargout=3)

But I got a wrong message

      File "/media/Data/MyModel/train.py", line 118, in <module>
    proj = eng.fanbeam(hello,1075.0,para_dic)
  File "/home/wd/anaconda3/lib/python3.7/site-packages/matlab/engine/matlabengine.py", line 71, in __call__
    _stderr, feval=True).result()
  File "/home/wd/anaconda3/lib/python3.7/site-packages/matlab/engine/futureresult.py", line 67, in result
    return self.__future.result(timeout)
  File "/home/wd/anaconda3/lib/python3.7/site-packages/matlab/engine/fevalfuture.py", line 82, in result
    self._result = pythonengine.getFEvalResult(self._future,self._nargout, None, out=self._out, err=self._err)
matlab.engine.MatlabExecutionError: 
  File /usr/local/MATLAB/R2019b/toolbox/images/images/private/check_fan_params.m, line 20, in check_fan_params

  File /usr/local/MATLAB/R2019b/toolbox/images/images/fanbeam.m, line 168, in fanbeam
Function FANBEAM expected an even number of parameter/value arguments.

So,What should I do to pass these arguments to fanbeam function from python?

[Matt J]

Note: For years, fanbeam has exhibited weird non-linear behavior, which nobody seems to understand. I wouldn't trust it.

https://www.mathworks.com/matlabcentral/answers/104551-why-isn-t-fanbeam-linear

Answer 1

[Shrinidhi KR]

You can just call it and specify the parameters directly, it worked for me.

import matlab.engine
eng = matlab.engine.start_matlab()
I = eng.eval('ones(100)')
D = eng.eval('200')
dtheta = eng.eval('45')
proj = eng.fanbeam(I, D,'FanSensorGeometry', 'arc','FanSensorSpacing',0.1,'FanRotationIncrement',dtheta)

I have used eval to avoid any datatype mismatch from matlab into python. Alternatively you can try to call fanbeam function inside eval function as well, but have to handle the string quotations properly

[dh tang]

thanks a lot :)