# How do I split long equations that have conditions or qualifiers?

I am writing few equations and it's coming out of column in overleaf.

$$Loss_{\text {de}}=\sum_{i=1}^{N_{\text {steps}}} \sum_{b=1}^{B} \sum_{j=1}^{D} \frac{-\mathbf{M}_{\mathbf{b}, \mathbf{j}}[\mathbf{i}]}{N_{\text {steps}} \cdot B} \log \left(\mathbf{M}_{\mathbf{b}, \mathbf{j}}[\mathbf{i}]+\epsilon\right)$$


$$X(k)=\sum_{n=0}^{N-1} x(n) w(n) e^{\frac{-2 \pi i k n}{N}}, \quad k=0,1, \ldots, N-1$$


and

$$\hbar_{k}=-\sum_{n=1}^{N-1}\left(\hat{s}_{k}(n)^{2}\right) \ln \left(\hat{s}_{k}(n)^{2}\right), \quad 1 \leq n \leq N-1$$


How can I modify those equations to make it looking good and small to fit in one column easily?

How to convert the first equation like this format?

(At the OP's request, I've edited my answer to provide a version of the first equation that places the limits of summation off to the right. Unsurprisingly, the result of this change is awful.)

• For the first equation, I suggest you omit the \left and \right sizing directives (they do nothing but inflate the horizontal spacing, replace \cdot with \,, change Loss to \mathrm{Loss}, and use a \smashoperator{...} wrapper on the first summation term (to let the upper limit of summation protrude into the left-hand space). Conversely, I would add a bit of whitespace between , and \mathbf{j} in order to avoid a visual collision of the glyphs.

• To place the limits of summation off to the right instead of above and below the \sum symbols in the first equation, simply change the 3 instances of \sum to \sum\nolimits (and remove the \smashoperator directive). Unsurprisingly, the equation no longer fits in a single line. Moreover, it just looks awful from a typographic perspective. But, as the saying goes, there's no arguing about tastes...

• For the second equation, I suggest using a 2-row multline environment, writing \exp(...) instead of e^{\frac{...}{...}}, and encasing the sum term in a \smash[b]{...} directive in order to reduce the distance to the next row.

• For the third equation, get rid of the \left and \right directives and get rid of the redundant parentheses around the first multiplicative term.

\documentclass[twocolumn]{article} % or some other suitable document class
\usepackage{mathtools} % for '\smashoperator' macro
\usepackage{lipsum}    % for filler text
\begin{document}
\lipsum[1] % produce a paragraph of filler text
$$\mathrm{Loss}_{\mathrm{de}}= \smashoperator{\sum_{i=1}^{N_{\mathrm{steps}}}} \sum_{b=1}^{B} \sum_{j=1}^{D} \frac{-\mathbf{M}_{\mathbf{b},\mkern1.5mu \mathbf{j}}[\mathbf{i}]}{% N_{\mathrm{steps}}\, B} \log (\mathbf{M}_{\mathbf{b},\mkern1.5mu \mathbf{j}}[\mathbf{i}]+\epsilon)$$

$$\tag{1'} L_{\mathrm{sparse}}= \sum\nolimits_{i=1}^{N_{\mathrm{steps}}} \sum\nolimits_{b=1}^{B} \sum\nolimits_{j=1}^{D} \frac{-\mathbf{M}_{\mathbf{b},\mkern1.5mu \mathbf{j}}[\mathbf{i}]}{% N_{\mathrm{steps}}\, B} \log (\mathbf{M}_{\mathbf{b},\mkern1.5mu \mathbf{j}}[\mathbf{i}]+\epsilon)$$

\begin{multline}
X(k)=\smash[b]{\sum_{n=0}^{N-1}} x(n) w(n) \exp(-2 \pi i k n/N), \\
k=0,1, \ldots, N-1
\end{multline}

$$\hbar_{k}=-\sum_{n=1}^{N-1}\hat{s}_{k}(n)^{2} \ln (\hat{s}_{k}(n)^{2}), \quad 1 \leq n \leq N-1$$
\lipsum[2-10] % more filler text
\end{document}

• Hi, I am using first equation and getting "undefined control sequence" error. Commented Sep 23, 2020 at 22:41
• Can you please take a look at edited question, how can I use N steps, B, D front of \sum as shown in new image? Commented Sep 23, 2020 at 23:01
• @AadityaUra - Please see Show inline math as if it were display math (and vice versa).
– Mico
Commented Sep 23, 2020 at 23:53
• @AadityaUra - On your first question: Did you load the mathtools package?
– Mico
Commented Sep 24, 2020 at 0:02
• Yes, I used both mathtools and mathptmx. Can you edit your answer to show an example How to make that new equation image small with N steps, B, D front of \sum to fit in one column easily? Commented Sep 24, 2020 at 0:56