Resize array, prevent boundary effect
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I want to write a script that can double the size of an array using part of the data, while the original array remains the center of the big array. I think selecting some part and flipping it will be a good idea. I wrote the following script, but need assistance on how to assemble the left, right, top, bottom and center of the array to create the double size. I will greatly appreciate help to achieve this.
% read single column data and reshape
bouin='bou.dat'; % in data
numcolumns=200; % nx
numrows=200; % ny
fid=fopen(bouin,'r');
bou=fscanf(fid,'%f\n',[numcolumns numrows]); %open, read in and store
fclose(fid);
% preallocate array with double size of the intial data
bou_doub=zeros(2*numcolumns 2*numrows);
% define the boundary layers to be added
tempa=flipud(bou_doub(1:(numcolumns/2) 1:numrows)); % upper boundary
tempb=flipud(bou_doub((numcolumns/2):numcolumns 1:numrows)); % lower boundary
tempc=fliplr(bou_doub(1:numcolumns 1:(numrows/2))); % right boundary
tempd=fliplr(bou_doub(1:numcolumns (numrows/2):numrows)); % left boundary
%write all the parts into the main array with double size
bou_out=bou_doub(
% reshape final array to single column
bou_final=reshape(bou_out(numcolumns*numrows,1));
% write final array to file
fid=fopen('bou_final', 'w');
fprintf(fid,'%6.2f\n',bou_final); %this opens and writes the output matrix (adding the mean gravity value substracted prior to the FFT) in a ASCII file with a single data column with gravity anomaly
fclose(fid);
2 comentarios
jonas
el 19 de Sept. de 2018
Can you also draw the blocks a,b,c and d in your picture?
I guess this row
%write all the parts into the main array with double size
bou_out=bou_doub(
is where you are stuck, i.e. you have all the pieces but don't know how to compile them?
Respuestas (1)
Stephen23
el 21 de Sept. de 2018
Editada: Stephen23
el 21 de Sept. de 2018
You could do this quite easily with two very simple indices:
>> A = [0,1,2,3;4,5,6,7;8,9,10,11;12,13,14,15]
A =
0 1 2 3
4 5 6 7
8 9 10 11
12 13 14 15
>> S = size(A);
>> H = fix(S./2);
>> R = [H(2):-1:1,1:S(2),S(2):-1:H(2)+1]; % row index
>> C = [H(1):-1:1,1:S(1),S(1):-1:H(1)+1]; % column index
>> B = A(C,R)
B =
5 4 4 5 6 7 7 6
1 0 0 1 2 3 3 2
1 0 0 1 2 3 3 2
5 4 4 5 6 7 7 6
9 8 8 9 10 11 11 10
13 12 12 13 14 15 15 14
13 12 12 13 14 15 15 14
9 8 8 9 10 11 11 10
>> size(B)
ans =
8 8
Note that this is quite efficient as it does not copy any of the data into temporary arrays.
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