How can I get LaTeX to apply line breaks in display math mode for a long equation?
I created a table of:
% \usepackage{booktabs} \begin{table}[] \centering \caption{My caption} \label{my-label} \begin{tabular}{@{}|l|l|l|@{}} \toprule & Actual Positive $(y_i=1)$ & Actual Negative $(y_i=0)$ \\ \midrule Predicted Positive $c_i=1$ & $C_{TP_i}=0$ & $C_{FP_i}=r_i+C^m_{FP_i}$ \\ \midrule Predicted Negative $c_i=0$ & $C_{FN_i}=C_{device_i} + C_{marketInvest_i} + C_{usage_i}-Downpayment_i$ & $C_{TN_i}=0$ \\ \bottomrule \end{tabular} \end{table} where
$C_{FN_i}=C_{device_i} + C_{marketInvest_i} + C_{usage_i}-Downpayment_i$ denotes the equation which is too long.
How can I split it e.g. like
$C_{FN_i}=C_{device_i} + C_{marketInvest_i} + C_{usage_i}-Downpayment_i$ When using align in the table
\begin{align*} C_{FN_i}=C_{device_i} &+\\ C_{marketInvest_i} &+\\ C_{usage_i} &-\\ Downpayment_i \end{align} the result is a compilation error in latex.
\begin{table}[] \centering \caption{Cost matrix proposed for telecommunication industry.} \label{tbl:tma-costmat} \begin{tabular}{@{}l|l|l@{}} & Actual Positive $(y_i=1)$ & Actual Negative $(y_i=0)$ \\ \midrule Predicted Positive $c_i=1$ & $C_{TP_i}=0$ & $C_{FP_i}=r_i+C^m_{FP_i}$ \\ \midrule Predicted Negative $c_i=0$ & \begin{align*} C_{FN_i}=C_{device_i} &+\\ C_{marketInvest_i} &+\\ C_{usage_i} &-\\ Downpayment_i \end{align} & $C_{TN_i}=0$ \\ \end{tabular} \end{table} 
\begin{align*}is paired with\end{align}.