# in the part assignment is not a symbol, create different matrices with a loop

Im trying to assemble new matrices from some previous matrices I have created, but I canĀ“t. What Im trying to do is the following:

1) I have different matrices:

K11e[1] = {{a, a}, {a, a}};
K11e[2] = {{b, b}, {b, b}};
K12e[1] = {{aa, aa, aa, aa}, {aa, aa, aa, aa}};
K12e[2] = {{ab, ab, ab, ab}, {ab, ab, ab, ab}};
K22e[1] = {{ca, ca, ca, ca}, {ca, ca, ca, ca}, {ca, ca, ca, ca}, {ca, ca, ca, ca}};
K22e[2] = {{cb, cb, cb, cb}, {cb, cb, cb, cb}, {cb, cb, cb, cb}, {cb, cb, cb, cb}};
K21e[1] = {{da, da}, {da, da}, {da, da}, {da, da}};
K21e[2] = {{ba, ba}, {ba, ba}, {ba, ba}, {ba, ba}};


2) Define 2 vectors, I will used them to assemble my global matrices:

L1 = {1, 2};
L2 = {3, 4, 5, 6};


3) With "Do" assemble n matrices (2 for this example) with the previous matrices

Do[
KE[z] = ConstantArray[0, {6, 6}];
KE[z][[L1, L1]] = KE[z][[L1, L1]] + K11e[z];
KE[z][[L1, L2]] = KE[z][[L1, L2]] + K12e[z];
KE[z][[L2, L1]] = KE[z][[L2, L1]] + K21e[z];
KE[z][[L2, L2]] = KE[z][[L2, L2]] + K22e[z];, {z, 1, 2}]


4) So Im expecting to get this matrices:

KE[1] = {{a, a, aa, aa, aa, aa}, {a, a, aa, aa, aa, aa}, {da, da, ca,
ca, ca, ca}, {da, da, ca, ca, ca, ca}, {da, da, ca, ca, ca,
ca}, {da, da, ca, ca, ca, ca}};
KE[2] = {{b, b, ab, ab, ab, ab}, {b, b, ab, ab, ab, ab}, {ba, ba, cb,
cb, cb, cb}, {ba, ba, cb, cb, cb, cb}, {ba, ba, cb, cb, cb,
cb}, {ba, ba, cb, cb, cb, cb}}


But instead Mathematica give me the next error:

KE[z] in the part assignment is not a symbol.


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You should use ArrayFlatten to build block matrices, for example
{{K11e[1], K12e[1]},

myFunc = ArrayFlatten@MapThread[List, {{K11e[#], K21e[#]}, {K12e[#], K22e[#]}}, 1] &