How to multiply 2 columns by a scalar number in MATLAB

Question

Muhammad 2013-9-19

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Dear All

Hope you all are keeping good.i need 4 columns [X,Y,Z,Volume]in excel and first of all i want to multiply X and Y columns by 0.09 and (Z column contains just one scalar (0.18) value) then want to multiply all these X,Y,Z coordinates to get Volume. the code i am trying is given below. any help is appreciated.

if true
[x, y] = find(handles.maskedImage ~= 0);
% here x and y are created in excel by code line.to calculate the volume. first multiply 0.09 by both columns to get X and Y.
X=times(0.09,x);
Y=times(0.09,y);
Z = repmat(0.18,[length(x),1]);
[FileName,PathName] = uiputfile('*.xls','Save data to spreadsheet');
Volume=times(X,Y,Z);
Data=[X,Y,Z, Volume];
xlswrite([PathName '/' FileName],Data);  end

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Muhammad 2013-9-19

yes, it works thank you.

Image Analyst 2013-9-19

编辑：Image Analyst 2013-9-19

No it doesn't. Think about what you are doing. Multiplying the x,y coordinates of every pixel in the selected region by the spatial calibration factor does not calculate the volume.

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Answer 1

Jan 2013-9-19

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https://ww2.mathworks.cn/matlabcentral/answers/87701-how-to-multiply-2-columns-by-a-scalar-number-in-matlab#answer_97280

在 MATLAB Online 中打开

X = 0.09 * x;
Y = 0.09 * y;
Volume = X .* Y * 0.18;

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Jan 2013-9-20

@Image Analyst: I'm physicist and therefore very free in the choice of the definition of the term "volume", "pixel" and "coordinates". It could be a sound volume for a generalization of acoustic sound waves in a high-dimensional space with a linear metric. Or the coordinates could have been transformed before by a difference of neighboring elements.

But without doubt you are right and for the standard definition of a spatial volume in the Euclidean 3D space this calculations are not correct.

@Muhammad: You have to check the results with known test data, e.g. a line (Volume==0), a sphere and a rotated cube. I focused on avoiding the failing times().

Muhammad 2013-9-24

编辑：Muhammad 2013-9-24

在 MATLAB Online 中打开

ok yes, i understand. listen what i want.

 i want to make GUI it will work as we contour some region of interest in the patient CT in Pinnacle treatment planning system and then calculate the dose and find mean,minimum,  maximum dose in that region.
But i have a image file and a dose file. i want to use these to calculate the maximum, minimum, and mean doses inside the contour region.i want to make contoure in the image and use that in dose to find the dose in that region and calculate maximum, minimum, and mean dose in that region.
 till now, i made a GUI i can open a image (there are 55 image Slices, i can open one at a time) on the axis then i can contour by imfreehand. i thoght if i have the all x,y cooridnates inside the region then i will find these coordinate in the dose file which is in excel for the same slice to calculate the mean maximum doses but it vain