if statement executing even when condition is false

Question

Pratik Sahoo 2023-3-1

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1921455-if-statement-executing-even-when-condition-is-false

编辑： Pratik Sahoo 2023-3-6

The if statement executes regardless of the condition (Axialloadcalculated < res). Axialloadcalculated is a 1x1 double, Axialloads(r) is the rth element of 1xn array. How do I make the elseif statement trigger?

res = Axialloads(r)
    for i = 0:1:round(eccu/strain_step_Moment) % Change curvature, from maximum to minimum
        Axialloadcalculated = 0;
        if Axialloadcalculated < res
            for j = 1:n_layers
                epsilon(1, j) = (eccu - i*strain_step_Moment)*(NA - (j-0.5)*layer_thickness)/(NA - cc - dt);
                Load_depth(1, j) = areas_cc(1, j)*fc_unconfined(fck_unconfined, epsilon(1, j), ecp, ecu) + areas_core(1, j)*fc_confined(fck_confined, epsilon(1, j), eccp, eccu) + areas_longitudinal(1, j)*fs(fy, epsilon(1, j), eu, Es);
            end
            Axialloadcalculated = sum(Load_depth)
            NA = NA + 1
        elseif Axialloadcalculated > res
            break
        end
        Load(r+5, i+1) = Axialloadcalculated;
        for l = 1:n_layers
            leverarm(1,l) = NA - (l - 0.5)*layer_thickness; % Taking moment about NA
            Moment_depth = (areas_cc(1, l)*fc_unconfined(fck_unconfined, epsilon(1, l), ecp, ecu) + areas_core(1, l)*fc_confined(fck_confined, epsilon(1, l), eccp, eccu) + areas_longitudinal(1, l)*fs(fy, epsilon(1, l), eu, Es))*leverarm(1, l);
        end
        Moment(r+5,i+1) = sum(Moment_depth);
        phi(r+5,i+1) = -(epsilon(1,1) - epsilon(1,n_layers))/(H - 5);
    end

2 个评论
显示无隐藏无

Walter Roberson 2023-3-1

在 MATLAB Online 中打开

If you put in a breakpoint at

for j = 1:n_layers

and you display

Axialloadcalculated - res

what do you observe? You should only get negative results; a non-negative result should imply that the elseif would be tested.

CAM 2023-3-2

The variable, res, must be a positive number, because for every iteration of "i", you reset Axialloadcalculated = 0. In the code posted above, res is constant, so the code will always execute the IF block (res>0) and never get to the ELSEIF block.

Should "Axialloadcalculated = 0" be moved above the for loop? It looks like an initialization statement to me.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Arka 2023-3-6

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1921455-if-statement-executing-even-when-condition-is-false#answer_1185900

在 MATLAB Online 中打开

Hi,

Axialloadcalculated = 0; is written inside the for loop. In every iteration, the value of Axialloadcalculated is getting set to 0. The value of res is getting set just outside the loop. So, if res is greater than 0, in every iteration of the loop, the condition if Axialloadcalculated < res is getting evaluated to true, and the code enters the first if block.

If Axialloadcalculated = 0; is an initialization statement, you can move it outside the loop, so that the value of it does not get set to 0 on each iteration.

The updated code is as follows:

res = Axialloads(r)
Axialloadcalculated = 0;
    for i = 0:1:round(eccu/strain_step_Moment) % Change curvature, from maximum to minimum
        if Axialloadcalculated < res
            for j = 1:n_layers
                epsilon(1, j) = (eccu - i*strain_step_Moment)*(NA - (j-0.5)*layer_thickness)/(NA - cc - dt);
                Load_depth(1, j) = areas_cc(1, j)*fc_unconfined(fck_unconfined, epsilon(1, j), ecp, ecu) + areas_core(1, j)*fc_confined(fck_confined, epsilon(1, j), eccp, eccu) + areas_longitudinal(1, j)*fs(fy, epsilon(1, j), eu, Es);
            end
            Axialloadcalculated = sum(Load_depth)
            NA = NA + 1
        elseif Axialloadcalculated > res
            break
        end
        Load(r+5, i+1) = Axialloadcalculated;
        for l = 1:n_layers
            leverarm(1,l) = NA - (l - 0.5)*layer_thickness; % Taking moment about NA
            Moment_depth = (areas_cc(1, l)*fc_unconfined(fck_unconfined, epsilon(1, l), ecp, ecu) + areas_core(1, l)*fc_confined(fck_confined, epsilon(1, l), eccp, eccu) + areas_longitudinal(1, l)*fs(fy, epsilon(1, l), eu, Es))*leverarm(1, l);
        end
        Moment(r+5,i+1) = sum(Moment_depth);
        phi(r+5,i+1) = -(epsilon(1,1) - epsilon(1,n_layers))/(H - 5);
    end