How do I delete cell elements from a cell array?

Question

Shahriyar Karim 2020-3-6

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/509473-how-do-i-delete-cell-elements-from-a-cell-array

回答： BobH 2020-3-14

My function is supposed to take in an Nx3 cell array of unknown variables and known parameters and output an Nx2 cell array of unknown variable and respective value.

The first column corresponds to K values, second to m, and third column to v

I am to use K=(.5)mv^2 to find each unknown

Example:

hw_i = [{'K'} {[5]} {[2]}
        {[50]} {[4]} {'v'}
        {[70]} {'m'} {[9]}]
hw_f = physicsHW(hw_i);
hf_f → [{'K'} {[10]}
        {'v'} {[5]}
        {'m'} {[1.728]}]

This is my code right now:

function [E] = physicsHW(vars)
a = [];
%K = (0.5)(m)(v*v)
for i = 1:length(vars)
rows = vars(i,:)
   for j = 1:length(rows)
       if ischar(rows{j})==1
           v = vars(i,j)
           a = [a , v];
           vars(i,j) = [] %error here: null assignment can have only one non-colon idx
       end
   end
end

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Sindar 2020-3-6

You can't delete individual cells from a matrix, but you don't need to for this problem. Instead, build a new matrix of the correct size (Nx2) and fill it iteratively

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

BobH 2020-3-14

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/509473-how-do-i-delete-cell-elements-from-a-cell-array#answer_420066

在 MATLAB Online 中打开

function kmvsolve
    hw_i = {'K',5,2; 50,4,'v'; 70,'m',9 };
    hw_o = physicsHW( hw_i )
end
function out = physicsHW( indata )
    out = cell(0);  % empty cell array that we can add to
    
    for cr = 1:size(indata,1)   % for each row
    
        syms K m v;  % start fresh
        
        % hard code column numbers
        if( ischar( indata{cr,1} ) )   
            letter = indata{cr,1};
            m      = indata{cr,2};
            v      = indata{cr,3};
            
        elseif( ischar( indata{cr,2} ) )
            K      = indata{cr,1};
            letter = indata{cr,2};
            v      = indata{cr,3};
            
        elseif( ischar( indata{cr,3} ) )
            K      = indata{cr,1};
            m      = indata{cr,2};
            letter = indata{cr,3};
        end
        
        val = solve( K == .5*m*v^2 );
        
        % Accumulate results in a cell array
        %  after converting symbolic to a numeric
        out(end+1,:) = { letter, double( val(1) ) };
        
    end
    
end