Answer not updating with changes in variables

Creating a pressure calculator app using app design.

I have an issue whereby the Reynold's Number is not updating when i change the density units.

Note the Reynold's Number is only calculated when a button is pushed.

During the first run everything works fine however if i decide to change units on the density field then push button again the reynolds number does not change

I added labels to confirm the values for density, velocity and diamter change.

however the reynolds number does not change on line 29, even though the individual values change.

the below code is for the push button

            FlowrateUnitsOne = ['m' char(179) '/hr'];
            FlowrateUnitsTwo = ['ft' char(179) '/hr'];
            FlowrateUnitscheck = app.FlowrateUnits.Value;
            app.FlowrateUnits.ValueChangedFcn;
            DensityUnits1 = ['kg/m' char(179)];
            DensityUnits2 = ['lb/ft' char(179)];
            DensityUnit = app.DensityUnits.Value;
            if strcmp(DensityUnit,DensityUnits1)
                Density = app.DensityofFluidEditField.Value;
            elseif strcmp(DensityUnit,DensityUnits2)
                Density = 16.0184634 * app.DensityofFluidEditField.Value;
            end
            if strcmp(FlowrateUnitscheck,FlowrateUnitsTwo)
                Flowrate = app.FlowrateofLiquidEditField.Value/(2.2046*3600);
            elseif strcmp(FlowrateUnitscheck,FlowrateUnitsOne)
                Flowrate = app.FlowrateofLiquidEditField.Value/(3600);
            end
            if strcmp(app.DiameterUnits.Value,'mm')
                Diameter = app.DiameterofPipeEditField.Value/1000;
            end
            if strcmp(app.DiameterUnits.Value,'inch')
                Diameter = app.DiameterofPipeEditField.Value*0.0254;
            end
            if selectedButton == app.NewtonianButton_2
                Area = pi*((Diameter)^2)/4;
                Velocity = Flowrate/(Density*Area);
                DynamicViscosity = app.ViscosityofFluidEditField.Value;
                app.Label.Text = sprintf('%d',Density);
                app.Label5.Text = sprintf('%d',Area);
                app.Label4.Text = sprintf('%d',Flowrate);
                app.Label2.Text = sprintf('%d',Velocity);
                app.Label3.Text = sprintf('%d',Diameter);
                ReynoldsNumber = (Density*Velocity*Diameter)/(DynamicViscosity);
                app.ReynoldsNumberEditField.Value = ReynoldsNumber;
                app.Label6.Text = sprintf('%d',ReynoldsNumber);
            elseif selectedButton == app.NonNewtonianButton_2
                Area = pi*((Diameter)^2)/4;
                Velocity = Flowrate/(Density*Area);
                ApparentViscosity = app.ViscosityofFluidEditField.Value*(8*Velocity/Diameter)^(app.FlowBehaviourIndexEditField.Value - 1);
                ReynoldsNumber = Density*Velocity*Diameter/ApparentViscosity;
                app.ReynoldsNumberEditField.Value = ReynoldsNumber;
            end
            if app.ReynoldsNumberEditField.Value > 4000
                app.TypeofFlowLabel.Text = 'Turbulent Flow';
                app.TypeofFlowLabel.Visible = 'on';
            end
            if app.ReynoldsNumberEditField.Value < 2300
                app.TypeofFlowLabel.Text = 'Laminar Flow';
                app.TypeofFlowLabel.Visible = 'on';
            end
            if app.ReynoldsNumberEditField.Value > 2300 && app.ReynoldsNumberEditField.Value < 4000
                app.TypeofFlowLabel.Text = 'Transient Flow';
                app.TypeofFlowLabel.Visible = 'on';
            end
        end

Answer 1

[Ajay Neeli]

app.FlowrateUnits.ValueChangedFcn updates the FlowrateUnits. But there is no such function for DensityUnits. Adding app.DensityUnits.ValueChangedFcn might solve the issue.