[hconel]

Hello there,
In GMSH, I am able to create a series of points using For loop. I know that people are using external scripts (Matlab, Fortran etc.) to generate files in the

Point(i)={x,y,z,c};

format from a data file (which is in x,y,z,c format). What I am trying to do is, use the data file directly in the .geo file without a format conversion. For that, I need to store the array in a variable in .geo file. Is there a way to do that?

Thanks in advance,
Hüseyin

[Flowkersma]

Hi Hüseyin,

I don't know how if it's possible to store 2D arrays in GMSH .geo format but you can store 2 or 3 1D arrays. Here is an example of a script which contains NACA 0012 coordinates as arrays. It also contains a for loop which creates points from the arrays and a BSpline from the points. Obviously, this would be very straight-forward by using the Python interface of GMSH.

Best, Mikko

x = {1.0,0.991677,0.980364,0.9672594,0.9527094,0.9371906,0.9211098,0.9047307,0.888199,0.871589,0.8549374,0.838262,0.8215722,0.8048727,0.7881664,0.7714554,0.7547412,0.7380253,0.7213088,0.7045932,0.6878796,0.6711694,0.6544637,0.637764,0.6210716,0.6043879,0.5877143,0.5710523,0.5544034,0.5377692,0.5211515,0.504552,0.4879725,0.4714152,0.4548821,0.4383756,0.4218982,0.4054527,0.389042,0.3726696,0.3563391,0.3400549,0.3238215,0.3076446,0.2915302,0.2754859,0.2595202,0.2436435,0.2278683,0.2122105,0.1966898,0.181332,0.1661718,0.151256,0.1366496,0.1224422,0.1087546,0.09573936,0.08357044,0.07241381,0.06238752,0.05353091,0.04580157,0.03909828,0.03329271,0.02825461,0.02386618,0.02002762,0.01665766,0.01369187,0.01108041,0.008785821,0.006781149,0.005048426,0.003577154,0.002362688,0.001403607,0.0006990502,0.0002434807,2.600131e-05,2.600131e-05,0.0002434807,0.0006990502,0.001403607,0.002362688,0.003577154,0.005048426,0.006781149,0.008785821,0.01108041,0.01369187,0.01665766,0.02002762,0.02386618,0.02825461,0.03329271,0.03909828,0.04580157,0.05353091,0.06238752,0.07241381,0.08357044,0.09573936,0.1087546,0.1224422,0.1366496,0.151256,0.1661718,0.181332,0.1966898,0.2122105,0.2278683,0.2436435,0.2595202,0.2754859,0.2915302,0.3076446,0.3238215,0.3400549,0.3563391,0.3726696,0.389042,0.4054527,0.4218982,0.4383756,0.4548821,0.4714152,0.4879725,0.504552,0.5211515,0.5377692,0.5544034,0.5710523,0.5877143,0.6043879,0.6210716,0.637764,0.6544637,0.6711694,0.6878796,0.7045932,0.7213088,0.7380253,0.7547412,0.7714554,0.7881664,0.8048727,0.8215722,0.838262,0.8549374,0.871589,0.888199,0.9047307,0.9211098,0.9371906,0.9527094,0.9672594,0.980364,0.991677,1.0};
y = {0.00126,0.002421811,0.003982079,0.005762782,0.00770723,0.009744292,0.01181606,0.0138865,0.01593654,0.01795702,0.01994386,0.02189533,0.02381076,0.02568989,0.02753259,0.02933869,0.03110797,0.03284008,0.03453454,0.03619074,0.03780792,0.03938518,0.04092147,0.04241557,0.04386613,0.04527161,0.04663031,0.04794038,0.04919976,0.05040625,0.05155744,0.05265072,0.05368329,0.05465216,0.05555408,0.05638562,0.05714307,0.0578225,0.05841969,0.05893014,0.05934906,0.05967133,0.05989147,0.06000362,0.06000152,0.05987849,0.05962734,0.0592404,0.05870947,0.05802584,0.05718031,0.05616342,0.05496573,0.05357861,0.05199553,0.05021437,0.04824084,0.0460927,0.04380301,0.04141953,0.03899781,0.03659002,0.03423525,0.03195587,0.02975941,0.02764309,0.02559815,0.02361286,0.0216745,0.01977036,0.01788831,0.01601718,0.01414714,0.01227025,0.01038132,0.008479151,0.006567428,0.004656927,0.002761035,0.0009055955,-0.0009055955,-0.002761035,-0.004656927,-0.006567428,-0.008479151,-0.01038132,-0.01227025,-0.01414714,-0.01601718,-0.01788831,-0.01977036,-0.0216745,-0.02361286,-0.02559815,-0.02764309,-0.02975941,-0.03195587,-0.03423525,-0.03659002,-0.03899781,-0.04141953,-0.04380301,-0.0460927,-0.04824084,-0.05021437,-0.05199553,-0.05357861,-0.05496573,-0.05616342,-0.05718031,-0.05802584,-0.05870947,-0.0592404,-0.05962734,-0.05987849,-0.06000152,-0.06000362,-0.05989147,-0.05967133,-0.05934906,-0.05893014,-0.05841969,-0.0578225,-0.05714307,-0.05638562,-0.05555408,-0.05465216,-0.05368329,-0.05265072,-0.05155744,-0.05040625,-0.04919976,-0.04794038,-0.04663031,-0.04527161,-0.04386613,-0.04241557,-0.04092147,-0.03938518,-0.03780792,-0.03619074,-0.03453454,-0.03284008,-0.03110797,-0.02933869,-0.02753259,-0.02568989,-0.02381076,-0.02189533,-0.01994386,-0.01795702,-0.01593654,-0.0138865,-0.01181606,-0.009744292,-0.00770723,-0.005762782,-0.003982079,-0.002421811,-0.00126};

p = newp;
For i In {0: #x[]-1}
    Point(p + i) = {x[i], y[i], 0, 0.1};
EndFor
BSpline(1) = {1:#x[],1};

[hconel]

Originally Posted by Flowkersma

Hi Hüseyin,

I don't know how if it's possible to store 2D arrays in GMSH .geo format but you can store 2 or 3 1D arrays. Here is an example of a script which contains NACA 0012 coordinates as arrays. It also contains a for loop which creates points from the arrays and a BSpline from the points. Obviously, this would be very straight-forward by using the Python interface of GMSH.

Best, Mikko

x = {1.0,0.991677,0.980364,0.9672594,0.9527094,0.9371906,0.9211098,0.9047307,0.888199,0.871589,0.8549374,0.838262,0.8215722,0.8048727,0.7881664,0.7714554,0.7547412,0.7380253,0.7213088,0.7045932,0.6878796,0.6711694,0.6544637,0.637764,0.6210716,0.6043879,0.5877143,0.5710523,0.5544034,0.5377692,0.5211515,0.504552,0.4879725,0.4714152,0.4548821,0.4383756,0.4218982,0.4054527,0.389042,0.3726696,0.3563391,0.3400549,0.3238215,0.3076446,0.2915302,0.2754859,0.2595202,0.2436435,0.2278683,0.2122105,0.1966898,0.181332,0.1661718,0.151256,0.1366496,0.1224422,0.1087546,0.09573936,0.08357044,0.07241381,0.06238752,0.05353091,0.04580157,0.03909828,0.03329271,0.02825461,0.02386618,0.02002762,0.01665766,0.01369187,0.01108041,0.008785821,0.006781149,0.005048426,0.003577154,0.002362688,0.001403607,0.0006990502,0.0002434807,2.600131e-05,2.600131e-05,0.0002434807,0.0006990502,0.001403607,0.002362688,0.003577154,0.005048426,0.006781149,0.008785821,0.01108041,0.01369187,0.01665766,0.02002762,0.02386618,0.02825461,0.03329271,0.03909828,0.04580157,0.05353091,0.06238752,0.07241381,0.08357044,0.09573936,0.1087546,0.1224422,0.1366496,0.151256,0.1661718,0.181332,0.1966898,0.2122105,0.2278683,0.2436435,0.2595202,0.2754859,0.2915302,0.3076446,0.3238215,0.3400549,0.3563391,0.3726696,0.389042,0.4054527,0.4218982,0.4383756,0.4548821,0.4714152,0.4879725,0.504552,0.5211515,0.5377692,0.5544034,0.5710523,0.5877143,0.6043879,0.6210716,0.637764,0.6544637,0.6711694,0.6878796,0.7045932,0.7213088,0.7380253,0.7547412,0.7714554,0.7881664,0.8048727,0.8215722,0.838262,0.8549374,0.871589,0.888199,0.9047307,0.9211098,0.9371906,0.9527094,0.9672594,0.980364,0.991677,1.0};
y = {0.00126,0.002421811,0.003982079,0.005762782,0.00770723,0.009744292,0.01181606,0.0138865,0.01593654,0.01795702,0.01994386,0.02189533,0.02381076,0.02568989,0.02753259,0.02933869,0.03110797,0.03284008,0.03453454,0.03619074,0.03780792,0.03938518,0.04092147,0.04241557,0.04386613,0.04527161,0.04663031,0.04794038,0.04919976,0.05040625,0.05155744,0.05265072,0.05368329,0.05465216,0.05555408,0.05638562,0.05714307,0.0578225,0.05841969,0.05893014,0.05934906,0.05967133,0.05989147,0.06000362,0.06000152,0.05987849,0.05962734,0.0592404,0.05870947,0.05802584,0.05718031,0.05616342,0.05496573,0.05357861,0.05199553,0.05021437,0.04824084,0.0460927,0.04380301,0.04141953,0.03899781,0.03659002,0.03423525,0.03195587,0.02975941,0.02764309,0.02559815,0.02361286,0.0216745,0.01977036,0.01788831,0.01601718,0.01414714,0.01227025,0.01038132,0.008479151,0.006567428,0.004656927,0.002761035,0.0009055955,-0.0009055955,-0.002761035,-0.004656927,-0.006567428,-0.008479151,-0.01038132,-0.01227025,-0.01414714,-0.01601718,-0.01788831,-0.01977036,-0.0216745,-0.02361286,-0.02559815,-0.02764309,-0.02975941,-0.03195587,-0.03423525,-0.03659002,-0.03899781,-0.04141953,-0.04380301,-0.0460927,-0.04824084,-0.05021437,-0.05199553,-0.05357861,-0.05496573,-0.05616342,-0.05718031,-0.05802584,-0.05870947,-0.0592404,-0.05962734,-0.05987849,-0.06000152,-0.06000362,-0.05989147,-0.05967133,-0.05934906,-0.05893014,-0.05841969,-0.0578225,-0.05714307,-0.05638562,-0.05555408,-0.05465216,-0.05368329,-0.05265072,-0.05155744,-0.05040625,-0.04919976,-0.04794038,-0.04663031,-0.04527161,-0.04386613,-0.04241557,-0.04092147,-0.03938518,-0.03780792,-0.03619074,-0.03453454,-0.03284008,-0.03110797,-0.02933869,-0.02753259,-0.02568989,-0.02381076,-0.02189533,-0.01994386,-0.01795702,-0.01593654,-0.0138865,-0.01181606,-0.009744292,-0.00770723,-0.005762782,-0.003982079,-0.002421811,-0.00126};

p = newp;
For i In {0: #x[]-1}
    Point(p + i) = {x[i], y[i], 0, 0.1};
EndFor
BSpline(1) = {1:#x[],1};

Thanks so much for the neat idea!
The thing is, I am trying to read the x-y data from a file, which is usually in column format, such as x_column, y_column. In your case, I guess my only option is to provide x and y data externally in separate files (one for x and one for y) in row format and then include them in the .geo file.

Example:

contents of x_coords.dat file:

1.0,0.991677,0.980364,0.9672594,0.9527094,0.9371906,................

Then in the .geo file:

x={Include "x_coords.dat"};

Although I am not sure whether or not Include can be used in that way.

[Flowkersma]

I would suggest using the API. Here is an example code in Python how to open a .dat file and create similar BSpline with it.

import gmsh
datFile = 'naca0012.dat'
gmsh.initialize()
model = gmsh.model
factory = model.geo

with open(datFile) as fin:
    for line in fin:
        try:
            x, y = map(float,line.split())
            factory.addPoint(x, y, 0)
        except ValueError:
            print("Skipped line: ", line)

factory.synchronize()
ids = list(range(1, len(model.getEntities())+1))
ids.append(1) # [1,2,3,...,N,1]
spline = factory.addBSpline(ids)
factory.synchronize()
gmsh.fltk.run()
gmsh.finalize()