Generate 1 matrix from 3 data columns

Question

Jess 2017-8-1

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/351173-generate-1-matrix-from-3-data-columns

评论： Chad Greene 2017-8-1

I need advice and hopefully someone out there can help me. I have 3 columns of numerical data with n rows. All three columns will always have the same number of rows, but this can range between 2 and 10000 for a given data set. The example shows the kind of data I'm working with, where the first column lists X-coordinates, the second column lists Y-coordinates, and the third column lists the measured value at that x,y pair.

Example data:

   X-Coord       Y-Coord        Data
00000       1.00000       0.12240
00000       1.00000       0.36649
00000       1.00000       0.11111
00000       2.00000       0.19834
00000       2.00000       0.56791
00000       2.00000       0.94876
00000       3.00000       0.22284
00000       3.00000       0.13486
00000       3.00000       0.00273

What I want is to turn Column 3 into a matrix like the one below

Data Output:

22284   0.13486   0.00273
19834   0.56791   0.94876
12240   0.36649   0.11111

I feel like it should be possible and relatively simple, but I'm running into trouble. I tried starting by building a square matrix, and filling it point by point but with more rows:

 Data = zeros(3)
 Data(1,1) = Data(7)
 Data(2,1) = Data(4)
 Data(3,1) = Data(1)

but this becomes cumbersome and time consuming as the number of rows increase. I was considering building a loop to read X, Y, and Data and fill the matrix point by point, but I'm not sure where to begin with that.

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Jan 2017-8-1

2
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/351173-generate-1-matrix-from-3-data-columns#answer_276398

编辑：Jan 2017-8-1

在 MATLAB Online 中打开

X = [1,2,3,1,2,3,1,2,3]
Y = [1,1,1,2,2,2,3,3,3]
V = [0.12240, 0.36649, 0.11111, 0.19834, 0.56791, 0.94876, 0.22284, 0.13486, 0.00273]
nX = max(X);
nY = max(Y);
R  = zeros(nX, nY);
R(sub2ind(size(R), nY+1-Y, X)) = V;

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

Answer 2

Geoff Hayes 2017-8-1

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/351173-generate-1-matrix-from-3-data-columns#answer_276397

在 MATLAB Online 中打开

Jess - if z is your third column, then you could do something like

flip(reshape(z, [3 3])',1)

We re-shape z from a 9x1 to a 3x3 array. We then transpose it (with the apostrophe) and then flip it in the first dimension to flip the order of elements.

i.e.

>> z            [
                  0.1224
                 0.36649
                 0.11111
                 0.19834
                 0.56791
                 0.94876
                 0.22284
                 0.13486
                 0.00273];
>> flip(reshape(z, [3 3])',1)
ans =
                 0.22284                   0.13486                   0.00273
                 0.19834                   0.56791                   0.94876
                  0.1224                   0.36649                   0.11111

2 个评论
显示无隐藏无

Jess 2017-8-1

Thanks for the quick response. I'm not sure why but I'm getting an error message saying "Undefined function 'flip' for input arguments of type 'double'." even though the help page for flip specifically lists double under the data types.

Chad Greene 2017-8-1

在 MATLAB Online 中打开

The flip function was introduced in 2013b. If you have an older version you can do

flipud(reshape(z,[3 3])')

But with that solution you have to be careful that the x and y coordinates are perfectly regular.

请先登录，再进行评论。

Answer 3

Chad Greene 2017-8-1

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/351173-generate-1-matrix-from-3-data-columns#answer_276396

在 MATLAB Online 中打开

I think you can do this with xyz2grid. Syntax is simply

Data = xyz2grid(Column1,Column2,Column3);

2 个评论
显示无隐藏无

Jess 2017-8-1

Thanks for the quick response, I've never actually used the File Exchange before. Do I need to save the matlab files in the zip folder to a specific directory?

Chad Greene 2017-8-1

Hi Jess,

Yeah, unzip the folder and put it somewhere Matlab can find it. There are a number of ways to do that, but the easiest is just to put the xyz2grid.m file in your current working directory.

请先登录，再进行评论。