Caption Error even it is outside of tabular

Question

\begin{table}[h!]
    %\centering

    \begin{center}%\caption{table}{Caption text goes here}
        \begin{tabular}{| l | p{6.7cm}|  p{5.7cm}|  p{4cm} | }
            \toprule
              Function & Equation & Derivative & Plot \\ 

            \cmidrule(r){1-1}\cmidrule(lr){2-2}\cmidrule(l){3-3} \cmidrule(l){4-4}
             Binary\\Step & $\mathnormal{f(x) = \begin{cases}
                \text{0}      &  \text{, for }x  < \text{0}\\
                x  & \quad \text{for }x \geq \text{ 0} 
                \end{cases}}$ &$\mathnormal{f(x) = \begin{cases}
                \text{0}      &  \text{, for }x  \neq \text{0}\\
                ?  & \quad \text{for }x \geq \text{ 0}
                \end{cases}}$ & \raisebox{-\totalheight}{\includegraphics[width=0.2\textwidth, height=25mm]{binarystep.png}}    \\ %\cmidrule(r){1-1}\cmidrule(lr){2-2}\cmidrule(l){3-3}
                %\raisebox{-\totalheight}{\includegraphics[width=0.3\textwidth, height=60mm]{binarystep.png}} \\
        %   Rectified linear unit (ReLU)
        %   &  
            % &    \cmidrule(r){1-1}\cmidrule(lr){2-2}\cmidrule(l){3-3}
        %   \raisebox{-\totalheight}{\includegraphics[width=0.3\textwidth, height=60mm]{binarystep.png}}
            \cmidrule(r){1-1}\cmidrule(lr){2-2}\cmidrule(l){3-3}\cmidrule(l){4-4}
            Picewise \\Linear & $\mathnormal{f(x) = \begin{cases}
                \text{0}      &  \text{, for }x  < x_{min}\\
                wx+b  &\text{, for }x_{min} \geq x \leq x_{max} \\ \text{1}      & \text{, for }x  > x_{max}
                \end{cases}}$ &$\mathnormal{f(x) = \begin{cases}
                \text{0}      &  \text{, for }x  < x_{min}\\
                w  &\text{, for }x_{min} \leq x \leq x_{max} \\ \text{0}      & \text{, for }x  > x_{max}
                \end{cases}}$ & \raisebox{-\totalheight}{\includegraphics[width=0.2\textwidth, height=25mm]{piecewise.png}}    \\
            \cmidrule(r){1-1}\cmidrule(lr){2-2}\cmidrule(l){3-3}\cmidrule(l){4-4}
            Bipolar & $\mathnormal{f(x) = \begin{cases}
                \text{0}      &  \text{, for }x  < x_{min}\\
                wx+b  &\text{, for }x_{min} \geq x \leq x_{max} \\ \text{1}      & \text{, for }x  > x_{max}
                \end{cases}}$ &$\mathnormal{f(x) = \begin{cases}
                \text{0}      &  \text{, for }x  \neq \text{0}\\
                ?  & \quad \text{, for }x \geq \text{ 0}
                \end{cases}}$ & \raisebox{-\totalheight}{\includegraphics[width=0.2\textwidth, height=25mm]{bipolar.png}}
        %\\ \bottomrule
        \\ \bottomrule
        \end{tabular}
    \end{center}\label{tbl:actfunc}\\
\caption-of{table}{Caption text goes here}
\end{table}