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How to fill Table with with for sentence?

Urban Gramc

Posted 4 years ago

So i have this code, and I have Fx and Fy as components of force vector and rx and ry as move vector (x,y components). I don't have any issue with Force vector, but i would like to fill rx and ry vector with this form of data for n components: rx1=l/2 * Sin [fi1], rx2=l * Sin [fi1] + l/2 * Sin [fi2] rx3=l * Sin [fi1] + l * Sin [fi2] + l/2 * Sin [fi3] and so on (I hope that pattern is recognizable, and for ry is the same only with cosines) To write this by hand would take me too much time, so I am trying to use for sentence, but I am assuming I would use at least two FOR sentences and I have no idea how to do that. You probably see where the problem is: each next element should have 1 element than the one before. Thanks for your help. Attachments: forum.nb

POSTED BY: Urban Gramc

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Bill Nelson

Posted 4 years ago

Can you adapt this n=3; rx=Table[Sum[If[j<i,1,1/2]ISin[Subscript[\[Phi],j]],{j,1,i}],{i,1,n}]; ry=Table[Sum[If[j<i,1,1/2]ICos[Subscript[\[Phi],j]],{j,1,i}],{i,1,n}]; and then rx has the value {(I/2)Sin[Subscript[\[Phi], 1]], ISin[Subscript[\[Phi], 1]] + (I/2)Sin[Subscript[\[Phi], 2]], ISin[Subscript[\[Phi], 1]] + ISin[Subscript[\[Phi], 2]] + (I/2)Sin[Subscript[\[Phi], 3]]} and ry is similar with Cos If you only wish to use For then n=3; rx=Table[0,{n}]; For[i=1,i<=n,i++, For[j=1,j<=i,j++, rx[[i]]=rx[[i]]+If[j<i,1,1/2]ISin[Subscript[\[Phi],j]] ] ]; will give you the same values for rx and similar code with Cos will give you the same values for ry

Can you adapt this

n=3;
rx=Table[Sum[If[j<i,1,1/2]*I*Sin[Subscript[\[Phi],j]],{j,1,i}],{i,1,n}];
ry=Table[Sum[If[j<i,1,1/2]*I*Cos[Subscript[\[Phi],j]],{j,1,i}],{i,1,n}];

and then rx has the value

{(I/2)*Sin[Subscript[\[Phi], 1]],
 I*Sin[Subscript[\[Phi], 1]] + (I/2)*Sin[Subscript[\[Phi], 2]], 
 I*Sin[Subscript[\[Phi], 1]] + I*Sin[Subscript[\[Phi], 2]] + (I/2)*Sin[Subscript[\[Phi], 3]]}

and ry is similar with Cos

If you only wish to use For then

n=3;
rx=Table[0,{n}];
For[i=1,i<=n,i++,
  For[j=1,j<=i,j++,
    rx[[i]]=rx[[i]]+If[j<i,1,1/2]*I*Sin[Subscript[\[Phi],j]]
  ]
];

will give you the same values for rx and similar code with Cos will give you the same values for ry

POSTED BY: Bill Nelson

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